回复：BILL纠纷问题，

1。 The service had been cancelled by them -since you didnt get any service after you paid them in full, so you dont own them anything. Tell them do whatever they like because you have the evidence.

2. you dont need to worry about collection agnet. if the collection letter comes, contact them and fax all your evidence to them. Actually you overpaid your bill and you have not get any service for that.

3. they cannot hurt your credit unless a judgment from court comes against you. It wont happen to you in this case.