A few people say they are overcharged for text messaging, and yet, THEY don't even know what the charges are, or if in fact the charges are invalid... and you want to jump all over it?
The billing system T-Mobile employs generally does not make many errors, as if it did something would've been done a long time ago. 18+ Million customers, there are bound to be mistakes in billing, as with ANY company.
I would not get too far ahead of yourself. First find out the facts....