Telkom: Do useless - you can't get rid of them

On the 3rd of August 2020 I informed Telkom by e-mail that I am cancelling my last line with them. I attached all the required documentation and received confirmation from them that they received my instruction. Today I receive an invoice from them? When I queried it they tell me that there is no record of my cancellation on the system!!! This is why we are cancelling the service - because there is NO service. I had 5 lines, which I have now cancelled - good riddance.