What are the APN settings for the Samsung (S-G530A) on Straight Talk AT&T?

[AC Question]

I recently bought an AT&T Samsung Go Prime, model number s-g530a. This phone is originally an AT&T Prepaid GoPhone, but is known to be usable on the Straight Talk AT&T network. I have the phone activated, however I think I have the wrong APN settings for it as I cannot send or receive picture MMS messages. I have tried the straight talk website and entered the settings found there, as well as settings found elsewhere on the Internet with no luck. Can anybody help me fix this issue? Thanks in advance!