Poor internet coverage and over billing

I signed internet data contract with CELL C August 2014 for R99.00 per month. Until this year April I was Bill R2.4.000. To my surprise I was told I over used, how can I over use for the very first time after 9 months of over using, and during contract I was clear that I can only pay R99.00. I expected the cell c personal to tell me about capping, with I did know then. April I went to wonder park to complain and the capped it by extra R50.00, however for the two months the bill is. Above the agreed capping , R156.00 ( I expected not more than, R149.00).<br> <br> I also have internet problem. About for months ago I went to cells that I not benefit from this contract because I spend data roaming searching for network, I can only use it if I far from home where couverage is better, I Need it when I home but I cannot use it. Were I get coverage is where I have access to WIFI and I don't need to use my data! It means I don't need to pay cell c for service I don't get. They have reference number for my network coverage problem I reported to them and is not yet solved.<br> <br> I wish not to continue with them. I will apply to different network that will cover me when am home.