Billed for service never installed or used

I'm getting billed for service that was never installed. This is affecting my credit record. I tried to cancel when I received my first sms that I will be billed pro rate. After I received an account in the mail I called again to stop the account with no luck! Ref ********** 7 This is unacceptable and would like this account to be canceled ASAP. How can you pay for something that was never installed and that I can't use!!