Cancellations of no service

I have been struggling for the past 18 months to cancel a Wifi Router on Vodacom's old system without any success. Contacting Cancellations on *** is useless since the operators either transfer you to the moon, cut your call or neglect to call back later, as promised. Customer Care is even worse, they insist you contact Cancellations. I have been paying 18 months for a service I don't use and I can't get cancelled. I am at the end of my rope!