I've got MMS working (Saint Clairsville, OH) after installing the AT&T 6.0 carrier file and a few calls to AT&T and one to Apple Care (transferred there from an AT&T call) and restoring the phone from backup. I'm running v3.0 and would like to know what I need to change under "Settings", "General", "Network" and finally "Cellular Data Network" to get tethering working? There are settings for "Cellular Data", "Visual Voicemail" and "MMS". By default, Cellular Data has "phone" in APN and Username and Password are blank. By default, Visual Voicemail has "acds.voicemail" in APN and Username and Password are blank. By default, MMS has "wap.cingular" in APN and Username and Password are blank. MMSC has "http://mmsc.cingular.com:80", MMS Proxy has "wireless.cingular.com:80", MMS Max Message Size "614400" and MMS UA Prof URL is blank.
I really don't want to loose my MMS after hours of finally getting it to work with v3.0 but I want to try tethering just out of curiosity. I assume I still have Visual Voice Mail as I did before but I haven't verified this as I haven't received any since updating.
Any help or settings would greatly be appreciated from someone who has this setup working.
iPhone 3GS v3.0
carrier file: AT&T 6.0 (thanks Mocque)
Thanks also to Savior1974 for the step by step update instructions.