Continuous Calling

For the last month I have told them I had coverage and after telling them I no longer own the vehicle and to remove my number, they still continue to harass me with the phone calls.  I still receive 8 - 10 calls daily.  I am ill and can not even rest for the phone calls.  I wish there was some way to make them remove my phone number from their robo-calls.  If there is a solution, will someone please let me know.