OK so i have been looking for some settings to work with this and att so i called att ad told them i have 2 phones which i do and one is a old nokia make sure they have that one down as the main phone you use then make sure the MMS on that phone works with your number. then just pop the sim into the iphone and make the settings as follows:
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the most important thin is making sure that pic messaging works on the other phone this means you can receive and send pics to another phone. To do this just pop ur sim in another phone and try sending it to urself if it doesnt work you need to call att and get it to work in the other phone. email me at firstname.lastname@example.org
with any questions i might be able to answer i know how it feels to look for an answer and try for hours and not get a working swirlyMMS so email me and i might be able to help.