It's not a MAC address......
The contract is no longer in place, you have materially breached it by refusing to pay for service for the whole 12 months. That means they are due damages. What those damages will be is very unlikely to be the same amount of money they would have got out of you had you continued to be a customer, though I sure they would settle for that. I don't know what the true figure would be you would need to talk to a lawyer/accountant/telecoms expert.