Originally Posted by Rukbat
You put an AT&T SIM into a TMobile phone, didn't change the APN, and you still get internet and MMS? Then someone has a server set up REALLY sloppy. A phone registered to AT&T's network should NOT be able to use TMobile's gateway or MMS server. I can understand the MMS server being set up loosely, but not the gateway.
I have an AT&T Note 3 that I unlocked onto T-MOBILE and I didn't have to touch apn settings at all for anything to work. Only thing I'm using is intelli3g for the automatic LTE, WCDMA/GSM switching.
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Future Phone: LG G Pro 2
Current Phones: Samsung Galaxy Note 3 AT&T [Unlocked to T-Mobile & Hashcode'd on KnoxRa1d]
Past: LG Optimus G Pro AT&T, LG Optimus G AT&T, LG Google Nexus 4, Samsung Galaxy S3 AT&T, Samsung GS2 AT&T, Sony Xperia ion AT&T, Samsung Infuse AT&T(First Android Phone), All iPhones before that.