Please give me an answer!!!!

I've had an internet contract with since 2012. In 2014 it stopped working Flamwood branch becuase I thought it's faulty. Johan(Manager)& Remo confirmed the ''stick'' is faulty, but they need the original receipt to send it away. I couldnt find it, so nothing could be done? I took a chance and went to Matlosana, Keitumetse helped me and laughed, because the only reason why not working is I need to upgrade, so I paid six months for nothing. We did the upgrade and I took the R79 contract 1GB. That was January 2015. But had problems, becuase I'm on for 5 min then I get a message, You have run out of airtime. I eventually took in the laptop as requested where they disabled some automatic updates or something. I also bought more airtime from Keitumetse. In June they deducted R410 and when I enquired why, they said I went over my 1GB limit. How is that possible if I was at the store numerous times for running out of airtime. I eventually asked to see the Manager Lizelle Meyer. At first she refused to come out cause too busy, but eventually did. Nobody can give me an explanation I've been waiting 1 month already. Billing enquiry logged ref***,whats going on?Answer/response Please!!!!!!