No communication from Vodacom

I accidentally paid too much money to Vodacom for my monthly installment. I phoned customer care and they said I should e-mail the proof of payment to ********** I did so and also sent follow up mails. Never heard anything from them. I did not even receive reference number, SMS or mail to say they have received my mail. I phoned again. They checked to see if they have received the proof of payment yet. This was seven days later - and..NO they do not even have the proof of payment. I had to send it again and also send it to their legal collections department. I made the payment on 29 January. I simply requested that they pay back what I paid extra. Today is 13 February. Despite my mails and phone calls I have not received any answer or response from Vodacom. I could not pay my rent or medical aid. Yes, it was my mistake but it has been so long and why can't they just respond?