You have to get on the phone with ATT and say hey i want WAP Push enabled on my phone, they will reply "Well you're using an iPhone we can't do that for you" but then you respond, "Well i switch out my sim card into another phone to take pictures for work/school/etc so i don't see why you can't just enable it since im not using an iphone for the pictures im using another, so can you please enable WAP Push?" once you get them to do it, have them reset your phone OTA, in doing so it resets you on the network, does no harm just a simple reset of your phone's network, but after you get off the phone with them turn off your phone and wait for like 2-3 mins so they reset it OTA, once you turn it back on it should work. However the hard part is getting someone to do that for you. I came across people that said "we seriously cant do that in our system..." which is a lie they can do it, they are just told not to. So you have to spend a while trying to find someone to do it for you without them knowing you are trying to send MMS on the iphone.