recycled number

I recently took a contract phone with vodacom and the cellpone number allocated to me was recently used by another person. Everyday I get calls, whatsapp messages from people enquiring about the previous user. This is really frustrating and affects my privacy. I called vodacom today to give me a new number but I was told this is not possible. Is it not possible to be allocated a new number or a recycled number that was last used long time ago? Please assist. I cant continue with this number.