Wont send text. says memory full

Hi
there was a common software fault on this model. Try a factory reset, but back up your information first! If this does not resolve the issue, do you still have Nokia Data Suite software that came in box with the phone? Load this disc into your computer and using the data cable supplied also with the phone, connect to the Data Suite software. In the Data Suite program is an option to update the phones software to latest version from Nokia. (back up you information first as software update will wipe your data!)
Otherwise if phone is still under warranty return to where you purchased who should be able to update software for you free of charge? Hope that helps?