Phone number deleted

I am very disappointed because after coming back from overseas after a year Vodacom deleted my phone number. I understand if there is no activity on the sim card in 3 months it gets blocked but I was never told by Vodacom after cancelling my contract and switching to prepaid in preparation of going overseas that they would just delete my number. I went to the customer care center in Canal Walk and the lady said there is no way that my phone number can be re-allocated to me, even though it is not in use by anyone else. I've been a loyal customer and want to continue with Vodacom as my service provider but I really want my number back. Please could you reinstate my phone number?