...messages online...? if they were erased from the phone itself? I believe they can view who you texted and when, but can they read the content of the text itself?
Providing records of text messages or other content violates privacy laws, so no cell phone company can do this without a subpoena- to the account owner nor anyone else. Also, messages are only stored on the servers for about a week.. You CANNOT go into a store and get records of the messages..