SHORT-CHANGED BY TELKOM: Deposit & Pro-rata Refunds

On the 18th February 2018 I Benson MUFUNDE paid for a DSL Service with Telkom. I paid a deposit of R700.00. I never missed any monthly payments against all invoices sent to me. Fast forward, on the 17th July 2020. I paid full settlement of my last bill with Telkom - *** This invoice covered period 15th July to 14th August 2020. Soon after this payment – 20th July 2020, I filed in a Service Cancellation which was accepted responded to by Telkom Reference Order ***A without conditions by Nomzikazi Komani; CEO HOTLINE, Email: *** On the 21st August I got a refund of the R700.00 paid as deposit and nothing of the Pro-rata element (26 days un-used part) of the Invoice A***; which, calculating from the monthly rental of R649.00 works out to be R562.38 My question/complaint is therefore two part: 1. My experience with deposits paid (elsewhere) is when it is refunded it is refunded with any and all the interest earned on it, save if it was or its portion used to settle an outstanding bill or something related to the service account. It would be beyond reason to believe Telkom received the deposit and stashed it in a money box somewhere in their offices where it did not earn any interest. I want my interest; Hello Peter can you please assist/guide? 2. Considering the service was terminated on the 20th July as acknowledged by the email message with the cited (above) Telkom reference, why then must I not get the un-used portion of my final payment. It is due to me and I must get it. Hello Peter please assist/guide so I can get what is due to me. It is a matter of PRINCIPLE and HONEST BUSINESS practice!