Nokia 5800 wont send text messages

check your message center number..

mot nokia cellphones have problems like that. fluctuating signal from the cell site to your cellphone maybe the cause of this problem. try resending it again by putting it into the draft section of your phone and try to resend it.

still this is not working then what to do ...........

CONTACT CUSTOMER CARE AND VERIFY YOUR MESSAGE CENTRE NUMBER IS CORRECT.

check SMSC number. if missing contact ur operator.

sounds like you got wrong setting ask your provider to send um or go online and look um up

try taking ur sim out then putting it back in this works for me when it happens (which happens 1/1000000 shot) or if you have pre-paid then you should check your balance. 

1. try turning phone off and on to reset, and try to send again
2. do you have good reception?
3. could be a temporary service adjustment, give it 10mins and try again
4. Could be a temporary phone network provider problem, or if CDMA phone, satelite could be down temporarily

you change settings for your massage

All you have to do is go to your message setting on your phone:
1. Open Messaging
2. On New message sellect options at bottom
3. Open settings
4. Open Text message, you should see: Message centre, message centre in use ect..
5. Open message centres this should go to next screen then open again, this screen should have : Message centre name & Message centre number (from your network provider you need to find out what is the message centres name & number are e.g in Australia it should be SMSC1 and number is +61411990001) then just manually enter these in there.