Shocking service received from Vuma

My WiFi goes off via debit order on the 1st of every month. In November, the debit order rejected due to no funds in my bank account. I then went onto my emails to check the invoices and made a manual payment into the indicated bank account but my WiFi was still not activated. I called Vuma the same day where they told me it’s the wrong bank account on the invoices and they will give me steps on how to get my WiFi reactivated again. Bare in mind this was a double payment I made. I asked about a refund and they told me it will take 21 working days to refund me. I AM NOW 2 MONTHS LATER!!! I called today and the agent took my details, shortly she told me “hold on the line” where she put down and sent me through to take a survey. I had to call a second time only be told that the manual payment I made is reflecting as a credit on their system but since November I was automatically debited whole time! At which point is my credit going to be used such that I don’t have to pay for one month or when will I be refunded? I have to call after Vuma and everytime the line is either distorted or some agent puts the phone down without providing me with a solution? I am spending unnecessary airtime!!