Cell C inexplicably high bill

I just signed up for the Cell C Lte- A router for 200GB at R859 on 25/01/2019. By the 27th my Data had been throttled. I called in and was informed it was pro ratad so I only received 40GB. I bought a bundle for my mobile router, unplugged the used up Lte-A router and waited for the 01st of the Month. A nominal amount went off my account and I figured, pro- ratad amount. I just got a bill for the end of Feb for R2500. When I called to ask how, the consultant told me about "usage" in out of bundles. Firstly the Data capped at the pro rata 40GB (called to confirm). Secondly, for safety reasons, the router was completely switched off until the 1st. Has anyone else experienced the same issue?