Requesting refund

I cancelled my subscription in April, but they are still deducting money from my account, they have been deducting monthly like I am still using their service, I am already paying for another service provider so meaning I am paying for two services, one which I am not using. The reason I cancelled is because there was no network coverage for 3 months straight so I am been paying for a service for 6 months and have never used it this is totally unacceptable!!!!!!