MTN forced contracts

I’ve been trying to contact their retention department for the past weeks but no one ever answers . I’ve been their customer for 4 years now and my phone contract has expired, the MTN plan however still continues and can only be cancelled by their retentions department which is never available to assist. At this point it feels like MTN if forcing their customers to stay on their expensive contracts , surely having this contract is not by choice if I can’t cancel it. This is exploitation