Here are some tips which might help.

The first thing to do is turn your phone off and on again - over 80% of all faults can be fixed by simply doing that.

Next, check how much memory you have left on your phone. If the memory is full or nearly full, delete some messages from your inbox and sent mail box.

How to check the memory on a Nokia:

1. From the Menu screen select Options
2. Scroll down and select Memory Details
3. Select Phone Memory

How to check the memory on a Sony Ericsson:

1. From the standby screen, select Menu
2. Select Settings
3. Select Phone status

For any other phone check your user guide. We have online versions here.

If you're sending a text message to someone abroad, check we have a roaming agreement with the network they are on by going to this page.

Reset the Message Centre number. We can send our message settings to your phone which will then be automatically updated. Go to this page and select your phone from the drop-down list, then Sending or receiving text messages (SMS). If you prefer to manually reset the Message Centre settings, the number should be: +447782000800.

Turn off call barring on your phone - this can sometimes help.

On a Nokia:

1. From Settings, select Phone
2. Select Call Barring
3. Select Outgoing Calls
4. Select Cancel
5. Select Incoming Calls
6. Select Cancel

On a Sony Ericsson:

1. From Settings scroll sideways until you reach Calls
2. Select Manage Calls
3. Select Accept Calls
4. Select All Callers

For any other phone check your user guide. We have online versions here.

Reset the settings on your phone. You will lose your personalised settings, like any changes you've made to your profiles or choice of wallpaper, but you will still have all your information, such as text messages, photos and ringtunes.

On a Nokia:

From the standby screen type *#7380#

On a Sony Ericsson:

1. From the standby screen, select Menu
2. Select Settings
3. Select Master Reset
4. Select Reset Settings

For any other phone check your user guide. We have online versions here.

If you're still having problems sending or receiving text messages, go to our online troubleshooter.