MTN, why?!

MTN is threatening to cancel my subscription because I defaulted on 1 payment which is R636. Yes, I negated to inform them that I was not able to make current with my account.I take full responsibility for that. Also, they’re threatening to take my account to the Lawyers if I don’t pay the cancellation fees of R13 120 in total. How is it possible to settle the latter amount yet I struggled to pay the former?! Also, there was no communication prior stipulating that my line would be disconnected or receipt of my June bill. I’ve been a customer for about 9 years and I have never experienced this type of service before.. I am disappointed.