why won't my Samsung Galaxy S5 download MMS

A

AC Question

I have a Galaxy S5. Yesterday I switched from Verizon service to AT&T, keeping the same phone. A picture message was sent to me today and has been trying to download for over 2 hours. This has never been an issue before. I have turned off phone and powered up again. Also I have turned off Wifi and turned on mobil data. still not downloading.