How can I report / block spam text messages on my T-Mobile iPhone?
You can report spam text messages to T-Mobile by forwarding the whole message to SPAM (7726). Text messages sent to the T-Mobile 7726 number are free and do not count toward your plan. iMessage spam should be reported directly to Apple.
Reporting spam helps your cellular provider identify and block spammers. The 7726 number is a joint mobile effort between AT&T, Verizon, Sprint and T-mobile to help eliminate spam.