Wrong Billing???

I am very upset because on my statement it says DUE -R310. I made a payment of R1000 last month when I only had to pay a bit more than R300. I got a SMS today stating I need to make a payment of R345. When I called your call center, the guy didn't know what to tell me and put me on hold, the call then just ended after being on hold for 2 min. Please sort this out as I paid the R1000 last month so I do not want to pay more than R300 a month. Please also take off the R99 protection plan as I have been trying to take it off without success anywhere.