Unless you're using your BT Mobile SIM with a brand new phone, it's highly likely that it'll be locked to the network of your previous mobile provider. Until it's unlocked, it'll only work with one of their SIMs.
To find out if your phone is locked, put your BT Mobile SIM into the phone and then turn it off and back on again. In general, if you can't see "BT" or a BT symbol somewhere on the screen your phone is probably locked. (On an Android or Windows phone you'll need to pull down from the top of the screen.)
You might also see a message saying something like:
- SIM Network Unlock PIN
- Enter Network MEP code
- Invalid SIM Card - Network locked SIM card inserted
- SIM not Valid
Watch a quick video on checking whether your phone is locked >
You'll need to contact your previous provider to get it unlocked.
Use the links here to see the different error messages for different makes of phone and to get help with unlocking them.
If your phone's locked, you'll see a message saying "SIM Network Unlock PIN" with a box to Unlock or Dismiss.
To unlock it, you'll need an unlocking code from your previous provider. Once you've put it in, your BT Mobile SIM should work.
If you dismiss the message, your phone will turn on but you won't be able to connect to the BT Mobile network.
If your iPhone is locked, you'll see a "SIM Not Valid" message as shown here or it may just say "No service".
You need to get in touch with your previous provider to get them to ask Apple to unlock it. Only your previous provider can do this.
Once it's done, if your iPhone has got iOS5 or earlier you'll need to plug it into a computer via USB and connect to iTunes to finish things off. If your phone has got iOS6 or later, then it's done over wi-fi or via the mobile network.
If this is the first time the iPhone is being used, you won't be able to get past the error message. If it's been used before with another SIM, then you can dismiss it, but you'll only be able to use the phone in airplane mode or without any SIM at all.
For more info go to the Apple support site > (opens a new window)
If your phone is locked you'll see "Network Locked – Please contact customer care" with an option to put in the "SIM network unlock PIN".
Once you've put in the unlocking code from your previous provider, the phone will unlock and your BT Mobile SIM should work OK.
If you ignore the error message, your phone will turn on but you won't be able to connect to the BT Mobile network.
If the phone is locked, you'll see a screen that says "SIM network unlock PIN" with the option to Unlock or Dismiss.
Once you've got the unlocking code from your previous provider, put it in on this screen. The phone will unlock and you'll be able to use your BT Mobile SIM.
If you dismiss the message, the phone will turn on, but you won't be able to connect to the BT Mobile network.
If the phone is locked, you'll see a screen that says "SIM network unlock PIN" with the option to Unlock or Dismiss.
Once you've got the unlocking code from your previous provider, put it in on this screen. The phone will unlock and you'll be able to use your BT Mobile SIM.
If you dismiss the message, your phone will turn on but you won't be able to connect to the BT Mobile network.
If your phone is locked, you'll see a message saying "This device is locked to a specific mobile operator".
Once you've got your code from your previous provider, put it in. Although it says you have 10 attempts, you'll find that the counter sticks at nine, and there's no limit on how many times you can try to put it in.
If you dismiss the message, your phone will turn on but you won't be able to connect to the BT Mobile network.
If your phone is locked, you'll see a message saying "SIM1 is not valid".
Once you've got your code from your previous provider, you need to type it in on this screen in the following format:
#pw+(unlock code)=7#
So as an example: #pw+21868062623681922314+7#
If you don't put a code in, your phone will turn on but you won't be able to connect to the BT Mobile network.
If your phone is locked, you'll see a screen saying "SIM network unlock PIN" with the option to Unlock or Dismiss.
Once you've got your unlock code from your previous provider, put it in on this screen and press Unlock. Your BT Mobile SIM should work OK.
If you dismiss the message, your phone will turn on but you won't be able to connect to the BT Mobile network.
If your phone is locked, you'll see a screen saying "“Please contact your OP to unlock your device".
Once you've got your unlock code from your previous provider, put it in on this screen. Your BT Mobile SIM should work OK.
If you ignore the message, your phone will turn on but you won't be able to connect to the BT Mobile network.
If your BlackBerry is locked you'll see "The device is MEP locked, contact your service provider" in various places (such as the lock screen, notification screen and BlackBerry hub).
Once you've got the unlock code from your previous provider, press one of the notifications to open the SIM settings screen.
Select Unlock network and put in the code. Your BT Mobile SIM should then work OK.
Be careful though. If you put in the wrong code more than 10 times, the phone will become permanently locked to the original provider.
If you don't unlock the phone, it'll turn on but you won't be able to connect to the BT Mobile network.