Change of Numbers/ Transferring airtime

I want to change my cellphone number which happens to be a top up contract number. Vodacom says I cannot do this, then I ask them can I transfer airtime from that number I do not want to use to my number I want to use and they say I cannot do that. Vodacom is forcing me to continue to use a number I do not want to use for personal reasons and safety reasons. I asked the consultant for reasons for this and he told me that it is not good business for Vodacom to allow us to transfer airtime as they will loose business. They say that If I have a contract and they allow me to transfer airtime my family and friends will not take out contracts as they can share in on my airtime. I asked if it is all about their benefit and did not care about clients needs and he said he will not debate this with me. he said all this with bad attitude.