You have had cell service for 10 years and never heard of early termination fees before?  In 20 years with Verizon, it was always in bold print when I got a new phone and signed a new 2 year contract.  $375 early termination fee

This is what happens when you break a contract, you have to pay off the balance.  It seems you have learned your lesson, as you are now waiting until all the other lines are out of contract before seeking new service.

Your new carrier will expect you to buy your own phone and pay for service.