Number porting

Hi

I hope someone can help me. I am wanting to get a contract from Cell C as their rates are so decent currently. I am currently on a Vodacom contract. I would like to know if anyone knows the process of porting your Vodacom number to Cell C and then having a new number allocated to your Vodacom contract. Is this possible? What's the best way to go about this?

Thanks in advance ;)