Rain useless service provider

Rain wifi internet when they started they were all good great service and all bit lately they are ***********,i was without connections end of november and they even send sms saying aboit interuptions ,i paid them R625 end november and in december i cancelled there services ,their payments are post paid i got disconnected on 26 december so i owe them R625 for services in december now they want 2 months payment for what ,***** them they uselesa