Galaxy S-3 with straight talk

[pathfinderse]

I recently bought an unlock att galaxy S3 BYOP, as st did not have any. Everything works except I cannot receive MMS or send any. I just downloaded the recommended handcent and all it did was copy my messages to the app. Does anyone have any other suggestions!!

 

[IAmSixNine]

Check your APN and make sure you have the correct gateway set up for MMSC.