Fixed Dialing Numbers (FDN) on Android: How It Works and Its Limits (2026)
NoDial Editorial ／ 2026-09-17Fixed Dialing Numbers, usually shortened to FDN, is a setting buried in the Phone app that turns your SIM card into a gatekeeper: once it is on, the phone can only call the numbers on a short list you approve. It is the opposite of a block list. This guide explains what FDN does and does not do, how to turn it on or off on Samsung and Pixel phones, what the PIN2 and PUK2 codes are, and why FDN is a poor fit if what you actually want is to stop calling one particular number while keeping the rest of your phone normal.
Steps are current as of September 2026. Menu names vary by phone maker and Android version. The default PIN2 depends on your mobile operator.
1. What FDN is, in 30 seconds
FDN is a feature of the SIM card, defined in the GSM standard. You store a list of allowed numbers on the SIM, switch FDN on, and from then on the phone will only place calls to numbers on that list. Everything else is refused before it dials. The list and the on/off state live on the SIM, so they follow the SIM into another phone.
Changing anything about FDN requires a second PIN called PIN2, which is different from the PIN you may enter when the phone starts. That is what makes FDN useful for a child's phone or a company handset: whoever holds PIN2 controls the list, and the person using the phone cannot get around it without that code.
FDN is an allow-list, not a block list. It stops every call except the ones you approved. That is exactly why it is powerful for a restricted phone and awkward for your own daily phone.
2. What FDN blocks, and what it leaves alone
| With FDN on | |
|---|---|
| Calls to numbers on the list | Allowed |
| Calls to any other number | Refused before dialing |
| Numbers starting with a listed prefix | Allowed on most phones (for example, listing a short prefix allows every number that begins with it) |
| Emergency numbers (112, 911, 999, 000…) | Always allowed |
| Incoming calls | Not affected: anyone can still call you |
| Text messages | Depends on the phone and operator; some devices also limit texting to the list |
| Calls made through apps (WhatsApp, Telegram…) | Not affected: FDN only covers regular phone calls |
3. How to turn FDN on or off on Android
FDN lives inside the Phone app's settings, next to call barring and call forwarding. You will need PIN2 (see the next section) for every change.
Samsung Galaxy
- Open the Phone app and tap the three dots (⋮) in the top right.
- Tap Settings → Supplementary services → Fixed dialling numbers. On a dual-SIM phone, pick the SIM first.
- Tap FDN list (sometimes shown as Manage FDN contacts) and add the numbers that should stay callable. Each addition asks for PIN2.
- Go back and tap Enable FDN, enter PIN2, and confirm.
To turn it off, return to the same screen, tap Disable FDN, and enter PIN2.
Google Pixel and phones using the Google Phone app
- Open the Phone app and tap the three dots (⋮) → Settings.
- Tap Calling accounts, then tap the name of your SIM.
- Tap Fixed dialling numbers.
- Tap FDN list and add the allowed numbers, entering PIN2 when asked.
- Tap Enable FDN and enter PIN2. To turn it off later, tap Disable FDN.
Other makers
Xiaomi, OnePlus, Oppo, Vivo and Realme phones put the same screen under the Phone app's settings, usually as Fixed dialing numbers or FDN inside Advanced settings or SIM card settings. The steps are identical: build the list, then enable with PIN2.
Add the numbers first, then switch FDN on. If you enable an empty list, the phone can call nothing but emergency numbers until you turn it off again with PIN2.
4. PIN2 and PUK2: the codes that guard FDN
PIN2 is a second PIN stored on the SIM. It is not your screen lock and not the SIM PIN that may appear when the phone starts. Your mobile operator sets the initial value; many use 0000, some use 1111 or print the code on the SIM's packaging. If the default does not work, ask your operator rather than guessing.
Guessing is risky because the SIM locks PIN2 after three wrong attempts. Once locked, the only way back in is PUK2, an unblocking code you get from your operator. If PUK2 is also entered wrong too many times, the FDN function on that SIM is permanently disabled and you will need a replacement SIM. So: ask, don't guess.
5. Why FDN is inconvenient for everyday use
- Everything not on the list is blocked. A new restaurant, a delivery driver, a call-back to a missed number: each one needs PIN2 and a trip into the settings before you can dial it.
- The list is small and clumsy. How many entries fit depends on the SIM, and editing happens inside a settings screen, not in your contacts.
- It is per SIM, not per phone. Swap SIMs and the restriction (and the list) goes with the old SIM.
- No schedules, no limits. FDN cannot say "only during work hours" or "three calls a week"; it is simply on or off.
- Whoever holds PIN2 holds the keys. If that person is you, FDN gives you no protection against yourself: you can switch it off in ten seconds.
That last point matters. FDN was designed so that someone else controls what a phone can call. It was never meant to help you keep a promise to yourself.
6. FDN vs. call barring vs. a per-number blocker
| Fixed Dialing Numbers | Call barring | Per-number blocker (NoDial) | |
|---|---|---|---|
| Logic | Allow-list: only these numbers | Category: all outgoing, international… | Block-list: not these numbers |
| Where the rule lives | SIM card | Operator's network | The phone |
| Code or password | PIN2 (from operator) | Barring password (from operator) | None |
| Schedules and limits | No | No | Days and hours, or calls per period |
| Undo | Instant with PIN2 | Instant with password | Takes effect one hour later; turning it back on is instant |
| Best for | A child's or work phone that may only call a few numbers | Stopping all or all international calls on a phone | Keeping yourself from calling specific numbers |
If your question is really about barring whole categories of calls, see our guide to call barring on Android.
7. If you only want to block calls to one number
Most people who look up FDN are not trying to lock down a company phone. They want to stop calling one number, or a few, and keep everything else working. FDN can do that only by listing every other number you might ever call, which is not realistic.
NoDial works the other way round. You add the numbers you have decided not to call; calls to those numbers end before they connect, and every other call goes through as usual. You can block a number all the time, only on certain days and hours, or after a set number of calls per day, week or month. There is no PIN to remember, and switching blocking off for a number takes effect one hour later, which is the point: it gives the moment of impulse time to pass. Emergency numbers can never be added.
Someone else controlling a phone → FDN. Stopping whole categories of calls → call barring. Stopping yourself from calling specific numbers → a per-number blocker.
8. FAQ
- What does "fixed dialing numbers" mean on Android?
- It is a SIM feature that limits outgoing calls to a list of approved numbers. With FDN on, the phone can only call numbers on the list plus emergency numbers.
- What is the default PIN2?
- It depends on your operator. Many use 0000, some use 1111, and some print it with the SIM. Ask your operator if the default fails; three wrong tries lock PIN2.
- What is PUK2?
- The unblocking code for a locked PIN2. Your operator provides it. Entering PUK2 wrong too many times permanently disables FDN on that SIM.
- Does FDN block incoming calls?
- No. FDN only restricts calls you make. Incoming calls are unaffected.
- Can I use FDN to block just one number?
- Not practically. FDN is an allow-list, so you would have to list every number you ever want to call. To block calls to specific numbers, use a per-number outgoing call blocker such as NoDial.
- Why does my phone say "Fixed dialing only" or refuse to call?
- FDN is on and the number you dialed is not on the list. Open Phone → Settings → the SIM's Fixed dialling numbers screen and either add the number or disable FDN with PIN2.
9. Summary
FDN turns the SIM into an allow-list guarded by PIN2. It is built for restricting someone else's phone, not for stopping yourself from calling one number. For that, use a per-number blocker.
- Allow-list on the SIM; everything not listed is refused; emergency calls and incoming calls are unaffected.
- Samsung: Phone → ⋮ → Settings → Supplementary services → Fixed dialling numbers. Pixel: Phone → ⋮ → Settings → Calling accounts → your SIM → Fixed dialling numbers.
- Build the list first, then Enable FDN with PIN2. Three wrong PIN2 entries lock it; PUK2 from your operator unlocks it.
- No schedules, no call limits, and instant undo for whoever holds PIN2.
- To block calls to specific numbers, on a schedule or with a limit, use NoDial instead.
Sources
- Wikipedia, "Fixed Dialing Number" en.wikipedia.org
- 3GPP Explorer glossary, "FDN (Fixed Dialling Number)" 3gpp-explorer.com
- EE device guide, "Turning fixed dialling on your Google Pixel 10 Pro XL on or off" deviceguides.ee.co.uk
- EE device guide, "Turning fixed dialling on your Samsung Galaxy S22 Ultra on or off" deviceguides.ee.co.uk
- Vodafone UK device guide, "Google Pixel 9a – Turn fixed dialling on or off" (default PIN2 1111 on Vodafone) deviceguides.vodafone.co.uk
- Optus device help, "Turn fixed dialing on or off – Samsung Galaxy A50" devicehelp.optus.com.au
Operators change their defaults and phone makers rename menus. Check your operator's help pages if a step does not match what you see.