Vodacom and RMCS *****

RMCS thru Vodacom changed my prepaid cellphone number to a contract number without my permission. Now i have no control over my number. How can i stop this if Vodacom doesnt want to help and this RMCS people will only help if i give them personal details. Why? They changed my prepaid to contract without my id why do they need it now?? Is there someone that can help me to sort this?