I have been with Cartrack for only two months

I have been with Cartrack for only two months. When Cartrack called me to arrange the installation of the tracker, I asked the operator whether there would be any pro-rata or upfront payment required. The operator assured me that there would be no charge and that the installation was free. At no point was I informed about any upfront pro-rata payment. I only became aware of this one month after the installation. As the months went by, Cartrack did not debit my account on the 27th as agreed. Instead, they attempted to debit my account twice in one month without my permission or authorization. Please assist I need the voice recording that i ask the operator about the upfront payment - pro rata