ACCELERIT live uncapped

After 2 years I've been with this internet service provider I moved homes and I canceled with them.This was on the 12th of July and they said I will get billed for a full calendar month which was then till 12 August,but then they sent me a bill till end of August.After I opened 2 tickets to complain,they sent me back that they confirmed the invoice has been canceled and they closed the tickets.Just after that they kept on sending me the same full payment invoice again.I opened another ticket which was only closed with no responce.I also tried numerous times to phone them.Or no answer or I get thrown off the line.