Telkom this is very bad service

I've been a paying customer for many years I think more than 8 years with telkom and due to unforseen circumstances I missed payment and my account got handed over I then made an arrangement to pay a certain amount and only to find out after 5 months of paying that the balance owing increased with thousands and the only option that one has is to settle with a discount of 15%... And if u unable to do so interest will forever accumulate even if you paying and u will start owing them more and more... They making it really difficult and I don't know what to do cause. I want to pay them off but nothing happens to the owing balance.... This is so unfair telkom has no mercy and this is ****************