Terrible Customer Service

I was double charged for my data contract, and when I logged a complaint a reference number was issued case was opened, and within two days the case was closed without being contacted to say how was the matter resolved because no one contacted me with the resolution. I contacted MTN telephonically, I was told that they had billed corrected, the issue was with one of their store consultant-Lucia (@Randridge Mall-JHB) that I took up the contract with. She was not transparent, she was supposed to tell me that I needed to have canceled my old contract, before upgrading to the new contract. That is was I was double billed. What t is so frustrating and upsetting about this matter, is that I now made to be the one at fault for actually having upgraded the contract when I did. MTN does not want to deal with one of their employees on this matter but they just want to take my money . I was billed in 1 June for May for data usage 26/05/2022 -26/06/2022 (Old Contract) and I paid for this bill , data was loaded on the 27th May I enough to cover the month of June. I was billed 1 July 2022 for June Data Usage 1/06/2022 -26/06/2022 (Pro-Rata) and was billed also 27/06/ 2022 - 26/07/2022 in one statement. The double billing is the period *** I had already paid for this charge on the statement issued end of May.