Refuse to pay back deposit

A contract for a month was signed in november and a rate for a 12month period was negotiated. No cancellation fee or alternative rate was mentioned or negotiated. The idea was to continue with the arrangement for a longer period, but I cancelled the deal after 2 month. Exeque car rental now refuse to pay back my deposit, because the deal was cancelled after 2months, <br> They also deduct etoll cost, which is clearly Exeque car Rental office admin mistake and hold me responsible for a key holder poorly glued.