Sounds like only the manager will be able to answer your questions. Poor coverage in key areas is often a good enough reason to get released from such contracts, but this needs to be highlighted early in the term. You mention it's been a long summer, so perhaps you did raise this early enough.
The phone is likely heavily subsidised (depending on the phone/ plan), so they will be entitled to reclaim it or charge you should you wish to keep it. The T&Cs of the offer you signed will likey state this.