Yes, you can sue foe the money. When someone enters into a contract for a defined period of time, he is obligated to make ALL the payments due under the contract for its entire length or duration unless 1) there is an early termination clause and he complies with its terms; 2) the other party (you) breached or violated the contract in some material or important way; or 3) the other party committed fraud (lied about something important to get the party that now wants out of the contract to enter into the contract in the first place. Otherwise, except as per 1) to 3) aboveb he is obligated for the full duration of the contract.