Help Having an issue Downloading/Sending MMS Picture and Messages

[Minib09]

I've had my phone for almost 2 years. I was on a plan with At&t and it was working just fine. I switched the At&t Go phone to save some money. I am now unable to download anything. From pictures to multi-messages. My siblings have the Iphones and they are also on the go phone plans. What am I doing wrong where I can't receive anything but a simple small text message.
I group messages, with the download screen, I try to download it, and yet it refuses to download. I can't download pictures either, so I don't know if its my phone, or just the plan that I am. But it doesn't make sense if its the plan because if its the plan then why does my siblings can receive pictures and multi-messages and I can't?
Please help.

 

[El Presidente]

Are you connected to WiFi? Try disconnecting, then redownloading.

You might also need to change your apn settings to gophone?

Settings -> More -> Mobile Networks -> Access Point Names. Do they still reference AT&T?

I'm not sure what the correct settings would be, you'd be better off calling gophone/AT&T for those.