Unable to cancel even when they can’t provide the service

After a month and a half of struggling with my connection and 1500 airtime spent on phoning I am still struggling to get proper internet connection. Today I want to cancel with immediate effect since my internet has been unusable for over a month and they just refuse. I sent mails bit no response. I dont know how to get rid of these people. Only option I can think of now is move houses and just stop their debits from going through. The support they provide is pathetic and I will be doing everything inmy power to let people know not to use this ISP