You can easily report or block the spam messages to T mobile. All you will need to do is forward the complete message to SPAM at 7726. The text message that you will send to T-Mobile 7726 number will be free of cost and you will not get charged. If you want to report iMessages, then report them directly to Apple customer support.
By reporting spams, you will only get the authentic messages and your device will report all irrelevant messages. The 7726 number is an effort made to report spams by AT&T, Verizon, Sprint and T-mobile.