Extremely Bad Service I ever experienced

I paid off Telekom, last year 27/06/2018, I paid R3000 as per settlement amount given by the consultant, I have a proof of payment for that, but they keep sending emails to say I owe them and that they will mess up my credit record, by handing me over to lawyers, the consultant who helped me is Haddy, on that day in June 2018 I walked into the Menlyn Telkom Store next to pnp, helped by Haddy, explained that I wanted to close my Telkom contract that I took few months ago due to the fact that they were not debating the amount we agreed apon but rather double, he gave me a settlement amount that I paid on the spot just next to them at pnp as per his advice, the same day I went back to him and he confirmed that the payment was reflecting and he closed the account /contract, he assured me that the account was closed and ill have no deductions anymore, and in did the deductions stopped until last month, to my surprise I received a bill from Telekom saying I now owe R400, I then went to the same store to try and understand what is going on, first spoke to Haddy who was now rude, I then spoke to the manager Onica Sitholo, they agreed that they at fault and will fix as soon as the statement comes out but to my surprise yesterday Telekom sent me onother invoice saying I now owe R1112. O8, how do I owe an amount which I paid off a year ago?,this is really making me upset, the extremely bad service just makes it worse, am sad really.