It is entirely possible for an internet provider to send a cusotmer an invoice months after one has moved out of the residence despite the customer having called and made a call to place a temporary suspension of the service. What you have is a classic dispute between a provider and customer where you need to speak with a person with the provider's account's receivable department to try and resolve the amount in dispute. What the provider is doing does not seem illegal per se with respect to the invoices you are receiving.