Many Samsung Jack I637 is AT&T branded. For non-AT&T customer, you will need modify the APN for data and MMS use.
Be default, the APN setting for AT&T is locked to guard accidental edition.
To remove the lock, you will simply go to Start->Applications->File Explorer to locate UAMgr.exe
- In File Explorer, you need to go up one level and then find the direct "Windows"
- Under \Windows, find UAMgr.exe
- Run UAMgr, and go to Menu->Tools->Unlock GRPS
- Now change the profiles "AT&T IMS" and "AT&T ISP" according to your own network.