Poor accounts management

Good day Vodacom

I trust this email finds you well as I am not well with the treatment I am getting from you guy. I am relating to the Accounts department, as I was called by one of their agent with an offer for a call, I had no issues taking up the offer. I explained to the guy whom was offering the phone that I would like you guy to take your money every month on the 25th. ever since the offer Vodacom has not taken their money on that day however they would take it on all different dates after the set date, sometimes its on the 7th or on the 14th depending on Vodacom's mood the may take it on the 2nd of the month. no problem however the problem starts when Vodacom starts making it look like I am in the wrong when they try and find no money. The first time this happen was last and they then debited twice on the following month as if I was in the wrong but then I did not mind now again you were suppose to take your money in November you did not and in December you took three time your money, Please can you advise as to what did I do wrong was i wrong by taking the offer every time I call in the accounts department I am told that "we working from home so the line so we cannot transfer you to the line manager" In this case what does one do because Vodacom is not fair. Please can someone help, I do not know what to do now?