How to make iPhone 4 send and receive picture messages?

I have already went to SETTINGS> MESSAGES> MMS MESSAGING is ON! Please don't suggest that because I've already done it and it didn't help.

Added (1). Okay, thanks so much! I called AT&T. The guy said the lady who helped me before had deleted my data package from when I had my Android and didn't add my data package for my iPhone. That's why it wouldn't send. Thanks to the first person who responded to this question!

You need to contact your service provider and check that GPRS is activated on your phone. In short, does internet work from your phone's network? If it does then MMS should work

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