Medicare - Cancellation of service

I have been with Medicare for some time but realized that the service is not what I need , i spoke to my bank and they advised me to write to Medicare first and cancel the contract which I duly did in October of last year - payment to stop from November. Medicare contacted me and for 20 minutes tried to convince me to stay with the company which I refused. I was put through to a dept who does what ever. since then I have continually getting demands for payment for a service which I am not only receiving but requesting,. I have written to Medicare again and again I am bombarded with phone calls and attempts to force me to pay for something I do not have. If they did not know I cancelled why did they call and insisted on a process ? I am sick and tired of this harassment and attempt to extort monies - please make it stop (tried to attach the email but your system does not allow me to do that )

what more do you want its been 5 minutes I am waiting for your response