MTN Data Contract

I have a data contract with MTN that I was told I’m going to pay R150 per month for 20gb data and I ended up paying more than that which is close to 500 , and now my services have been cancelled , they don’t answer calls and don’t even send invoices, I only got an invoice the first month . I can’t recieve calls or sms because I can’t afford to pay those ridiculous amounts they’re asking for . MTN is the worst service provider one could ever ask for