Poor/Bad Service from Vodacom

I had a cellphone contract with Vodacom which I requested premature cancellation which I made payment on the 15/03/2018. I also sent them proof of payment on the same day. The only contract I have with vodacom is for my WiFi router. To my surprise, Vodacom did not process my request and a result I am told that my account is arrears. I made several follow ups with Vodacom and I was told the amount of R2500 was taken as an advance payment. I am still trying to sort out the problem and the no one is able to give me a proper answer what really happened and how come there was no debit on my account. Instead I am dealing with rude and unprofessional Contact Centre Agents who decide to transfer my calls to unanswered lines. What a bad service.