I bought a sharp fx plus ATT phone unlocked through groupon about 2 months ago. I am trying to use it on the tmobile network. Calling is fine, however I have a problem with texting. If i remove the apn server for mms texts, regular texts work. If I put in the APN server, MMS messages work fine, but regular texts stop working. Does anybody have a suggestion on how to get this to work? It tries to send, and then after a minute says 'error code 1'. The sim card works fine in another phone. It has never worked properly.