Gatvol! Three calls later and still no resolution on incorrect debit amount!

I recently became a Vodacom customer after having an extremely successful relationship with another service provider. My mistake. After debiting my account correctly the first month, they subsequently doubled my debit amount in the second month. After calling them 3 times - being promised call backs by two agents and having one agent tell me he would transfer my call but dropped the call instead - I am gatvol. I just want my refund! How difficult can this be????? Also, your chatbot is silly - I have a data sim. It sent a pin to the data sim which is in a router. How do I get the pin to verify who I am?????