You have to inform any organization, utility company, business, etc. that you have a legally-binding contract with of the name change and provide that paperwork to them with-in one week of the change to maintain coverage of previously-existing contracts. Failure to do so can result in a breach of contract in many instances. In many instances companies add in clauses giving you up to a month to do so and they won't penalize you since they do understand that you may not know what to do or even remember to do it. In this case, lacking knowledge on when he did so and the fact Tim found out only because Tonka sent in paperwork with a different name on it, he's in breach of the contract because of it. They didn't know, and Tim makes it sound like Tonka said he wasn't going to tell them because he didn't think he had to.