Lack of expliantion and difficult process

I am trying to cancel my cell c contract which comes to an end at the end of this month. Bridgette tells me as I am busy porting my number to Vodacom they can not cancel my number. When I asked her to explain why she kept saying that it is because I am porting my number. I asked her repeatedly what does this have to do with anything a I still want to cancel my contract. She failed to explain the process on her side. She further tells me that I will still pay for January as I need to give 30 day notice. YOUR RETENTIONS LINE WAS NOT OPEN YESTERDAY WHEN I CALLED. I want to cancel my contract and retain my number.