Airtel — Internet bill related

We had paid a certain amount for one year of internet services to airtel but since then they have tortured us by calling us every month and irritated us by asking us for money and saying that we have an outstanding bill. We have cleared this issue with them more than 50 times but every month a new person calls us and we have to repeat the same issue and talk to them for half an hour and half the time they understand and half the time they don't so we have to repeat ourselves again and again but still nothing has been resolved. We have emailed them hundred times and we have proof also but still they have been torturing us since half a year. I hope that we can resolve this issue and get a compensation from the company. As the company is very huge and as there motto is providing good support to customers but they are just not doing it.