I recently purchased an unlocked HTC Inspire on AT&T on Amazon as I was tired of the prepaid phone selection that T Mobile offers. Anyways I just put my T Mobile SIM in the phone and all worked great. I however had to set up the APN for data to be used through customer service. For some reason my service must be sporadic in that it switches from AT&T and T Mobile when I loose all bars. It may be on T Mobile service and than when all bars are gone the AT&T will take over and Vice verse. Anyways my T Mobile data will not work when the AT&T is being used. I tried entering an APN for AT&T though various websites and was able to get it to work for a short time, but than it stopped and the APN was gone. Only the t mobile was still listed. I went back to the website and entered the information exactly as it showed and with trial and error as soon as I changed the MNC setting and went to save the APN it said "Saving" and still the T Mobile one was the only one showing up. Can anyone help with this as it is a pain to activate the t mobile network all the time as it seems that the AT&T network is stronger and is the default most of the time (and yes my service with T Mobile works when this happens). Here is the website I found the information from Internet Settings / APN Settings / MMS Settings
If you scroll about half way down to the United States for the AT&T network these are the settings I used:
Name: AT&T
APN: pta
Proxy:
Port:
Username:
Password:
Server:
MMSC: http://mmsc.mobile.att.net/
MMS Proxy: proxy.mobile.att.net
MMS Port: 80
MCC: 310
MNC: 410
Authentication Type:
APN Type: default,admin,fota,mms,supl,hipri
APN Protocol: IPv4/IPv6
APN Roaming Protocol: IPv4/IPv6
Please help thanks