Terrible customer service

Disappointed and beyond frustrated. During 2019 took out a phone contract and made monthly payment . During 29/07/2021 I requested an outstanding balance and was given an amount of R531.25. On 02/08/2021 I pay an amount of R300 and on 11/08/2024 I pay a further amount of R300. Three years later during November 2024 I was contacted by a law firm regarding my outstanding account. I sent all correspondence (which was also send to Mr Price Mobile Support) as proof that account was paid in full. I made a follow up with Mr Price Mobile Support and to my surprise they told me that I did not request a cancellation. None of their agents ever informed me if I paid my account in full that I must request a cancellation. Mr Price Mobile if this matter is not sorted soon I will make you very famous