billed for a service that was never delivered

I upgraded my prepaid to a contract line on the 19th of January. I was told activation on the new sim will be done in 2 to 24hrs.<br> <br> End of month there send a bill for January but up to now (4 February) the line is not activated and I am not able to use the service they are charging me for.<br> <br> Several trips to the MTN shop in Greenstone and countless calls to their call centre the new SIM is still not activated and MTN is refusing to reverse the amount they invoiced me in January.<br> <br> <br> Very Angry!