Surprise bill added onto account - no explanation

We received a surprises bill of R15 000 added onto our account about 6 months ago.<br> We have called and email for find out what this is for and have it removed, but to this day, no-one has ever responded with a concrete answer of what this bill is for. Instead, additional interest is being added each month and we keep being sent from pillar to post. Such bad service I have never seen before.