If you are a postpaid user.  You can login to your my.T-Mobile.com account and review the numbers you have texted and received texts from for that period of time and also print the, if necessary.  If you are a prepaid user.  The system does not generate a bill because you pay in advance, so no usage is stored.  If you want the contents of the actual text messages.  T-Mobile does not store the contents of text messages unless directed by law enforcement with a warrant.