Very very frustrated customer. Bad customer service. *****ing my money

Very very bad service received from Vodacom and Vodacom Customer care. I upgraded on the 3rd of February 2017 which was 2 months premature and my first handset instalment for my new device was deducted at the end of February together with my previous handset instalment which haven't yet expired. The handset instalment is supposed to be paid off over 24 months with the subscription fees still being deducted until the contract expires on 4 April 2019. My problem however is that if I started paying my first handset instalment at the end of Feb 2017 then the last instalment (of 24) should have been at the end of January 2019 but Vodacom has been deducting extra handset instalments for March, April, May and also June for which I have been invoiced. I have called customer care about 6 times and also called head office to no avail. Eventually on Friday I was called back by Zolelwa Bunyula, a representitive of Vodacom and she just wouldn't listen stating that the contract is for 24 months and that I am insisting on paying only for 21 months even after I tried explaining that 24 months have long since lapsed. Her solutuon to the problem is that I should not upgrade prematurely and that I should read the contract. I did read it and I do understand how it works but a handset instalment is only 24 months and has to be paid for for the full 24months since the upgrade. I asked to speak to her manager but she insisted that he was not available. Today I called her again and she said that she had spoken to him and that they both agree that the debits were correct. She wouldn' let me speak to him or even give me a name. Vodacom needs to refund me for the extra 5 months worth of handset instalment (5 x R400 = R2000). I am sick and tired of trying to explain this to them. Also I find it discomforting that there are no Afrikaans speaking consultants available to talk to. I have been a loyal customer of Vodacom for the last 8 years and want my queries handled in my mother tongue. Two of the consultants I have spoken to have taken down my details to request Afrukaans assistance from Customer Care in Cape Town but until now I have not received a response. Very very frutrated and unhappy customer.