Transfer from Nashua mobile done incorrectly

I would like to inform you that I am being billed incorrectly. I signed two identical two year contracts with Nashua Mobile for Samsung Galaxy S4s' on straight-up 100 with additional 1GB of data per month per number in May 2013. The total cost of both contracts was R798.00. When Altec Autopage Cellular took over the clientele from Nashua Mobile in November 2014, you did not capture the contract details correctly. According to your statements I took out two contracts for two BlackBerrys' 9720 with bis on straight-up 100. I did not notice this mistake until I saw a debit order in April 2015 for R1470.94. I was charged for using out of bundle data. What I find truly odd is that when I request my balances on both phones it says I have more than ample data, sms-es and available minutes left. Why then was I charged for data and airtime if I have minutes and data left? I would like you to fix this mistake of yours and refund me all the money I was overcharged for since November 2014. I already contacted your call centre to change both my contracts to prepaid as soon as my contracts are finished in May 2015. Please verify this. My two cell phone numbers are *** and ***