To be billed for service I cannot use.

I have been a loyal customer of Cell C for over 5 years. I am disgusted at my experience regarding a Data contract that I have will Cell C. For the first year or so I was able to use the SIM in my laptop without a problem, but for the past year I have been unable to use it due to there not being any signal. I went into a branch to explain this to them and I was told that they would send out a technician to check what the problem is. This never happened. Last month my contract which I paid R99 for should have ended however my account was debited with R279, as it has been moved to a month to month contract. According to Ameila(call centre agent) an sms was sent to my data sim, on which I have no signal, notifying me of this. She then goes on to tell me that I will be billed R279 up till May 2015 due to the 1 month notice that needed to be given. She explained the only way to prevent this is to renew the contract. So the only solution I have is to renew a contract that I cannot use due to the Cell C pathetic signal. Unbelievable.Once my cellphone contract expires I will never use Cell C ever again and will tell everyone I know not to either.