Unfair treatment after they signed me up

I had a 24 month data contract with Autopage and it expired in June 2015. They contacted me numerous time to renew and I eventually accepted. This is a data package ONLY, no device. Before the contract expired, the service was working fine, I never experienced any problems. After they upgraded it, it totally stopped working. Since July the 1st, I have never had a connection with this line. Yet, Autopage bills me month on month. I have made numerous attempts to have this fixed...I have driven in to the branch, made countless phone calls to the call centre, even took my device in for a diagnoses to make sure its not the device which is faulty. I have not used my device since the upgrade because it is always \offline". I get billed every month and they even double billed me by mistake which they also took long to rectify. They refuse to assist me now"