Bad service

Glocell service is the worst by far....

I called now to find out when my contract done, I am not even offered an upgrade as I am due for one, no specials are sent to me, no notification is sent to me to notify me that I am due for an upgrade. I want to place notice that my contract must be cancelled now as I am not interested in renewing it but no one can assist! how do I cancel this contract????