Check your contract

If you don't tell company, of course you will have big trouble when you go back USA later.

If you cancel the cell phone plan, you only need pay about $175 close fee for one phone. You also can let others take over your plan, then you don't need pay anything.

However, someone mentioned that you may not need pay close fee if you leave USA. Call custom service to figure it out. Read your contract (term) carefully will be greatly help.