Verizon phone with Straight Talk service and AT&T SIM card, will not send/receive MMS.

[AC Question]

I have the Galaxy Note 3 SM-N900V. It was previously on Verizon service, and I switched it to Straight Talk when it was given to me because that's what I've always used. My SIM card is for Straight Talk/AT&T, not sure if that matters. But I cannot send or receive MMS and am wondering if APN settings can be changed to fix this. I'm currently using the Straight Talk recommended settings.