Useless billing department

Hi, once again Telkom is showing how useless they are. I've cancelled my landline on the 26th of February 2018 online and by submitting it via email. I've received confirmation that they've received my cancellation. On the 15th of March I received an invoice where they overcharged me. I've logged a billing dispute Ref: ********** 1. No one bothered to phone me, typical from Telkom. On the 14th of April I once again received an invoice where they charged me additional fees as well. I phoned them but they were unable to assist me and created another dispute Ref: ********** 7. Another month went by without customer feedback. Today I received ANOTHER INVOICE. I can't understand how these useless idiots are still in business. No wonder they are losing customers. I will not recommend their pathetic service to anyone.