Outrageous tollgate charges

I have just received a statement from Roads Agency, which shows amounts charged for passing through the tollgate to and from Johannesburg. The invoices for tollgates initially ranged between R12 and R50 when at the time when I was driving my Nissan Pathfinder (02/02/2014 - 04/10/2014, some of which I settled.<br> <br> Later when I was driving a Mercedes Benz E-Class, the invoices received for passing through tollgate ranged between R7 and R400 (with high charges of R380.42, R301.39, R189.39, R107.02, R93.91, R84.45, etc). I cannot comprehend how I could be charged each of the high amounts when passing a tollgates. Why these amounts are so different from the ones incurred when I was driving a bigger car, Nissan Pathfinder???<br> <br> I called the Roads Agency office for clarity, and someone indicated she would ask on my behalf details about these extremely variable charges.<br> <br> I therefore request that you talk to Roads Agency to explain the discrepancy in this regard.<br> <br> Regards<br> Dr Thiambi Netshiluvhi<br> Tel: ***<br> Mobile: ***