Over billed by debit order on fixed top-u contact

Last year December 2014 I took out a top up contract of 2 Gb data for 24 months for the amount of R119 per month. For only three months I was billed for R119. On the 29 May I was debited for the amount of R139. There after I was billed for R129 for four months. On the 30 Nov 2015 all of a sudden a amount of R200.71 was deducted from my bank account. I went the the Gezina branch on the 4 Dec 2015 to sort out my account. The lady log a request at head office for them to sort out my account. I asked her If they will send me a ref number on my email that they will sort out my account. Till 11H23 this morning I did not receive an email. How can the company deduct any amount from my account as they please. The lady also told me that a credit will be passed on my account and that the company is not going to pay the money back in my bank account. My husband also had the same problem with Altech Autopage.