My nokia 6680 is unable to send text message, how do i fix it?

Hi,

Please check the message centre number is correct. To get the correct message centre number call your service provider customer care,they will provide you the number. please save this number as your message centre number.

Second thing you have to check weather reply via same message centre is put to NO.

To access these options follow the steps

Menu--->messages----->message settings---->text message--->service centre number.
select service number and enter the number you got from the service provider and save it.
Select this number in message centre in use

Please put reply via same centre to NO.

thanx