How to Cofigure MMS Picture Messaging & Data for an H2O iPhoneby Andrew McClain
If you want an iPhone, but do not want to spend as much money on a full two-year contract, you can look into services like H2O wireless, that lets you use your unlocked GSM iPhone under pay-as-you-go deals, instead of contracts. While this is a good solution for some, you might have to do some configuration work on your own. If the automatic configuration does not work, you need to set up your phone for MMS messaging through the Settings app.
Tap "Settings," then "Cellular," and tap "Cellular Data" if it is not already in the "On" position.
Scroll down and select "Cellular Data Network." This option will not appear if your iPhone is locked to another carrier.
Scroll down to "MMS" and tap it to change the settings. For "APN," type "att.mvno". Do not include quotation marks or period.
Type "http://mmsc.cingular.com" without quotation marks under the "MMSC" field.
Tap "Settings" to go back to the menu and tap "Messages." Scroll down and tap "MMS Messaging" to activate MMS Messaging on your phone.
Turn off your iPhone and reactivate it to apply the changed settings.