Vodacom *****s airtime

I have a Top Up 315 contract with Vodacom for a lot of years now and my airtime have accumulated over the last two years to a total of R1800.00 as I am not the talkative type of person spending every sent of airtime on my phone. So now I am due for an upgrade. Now Vodacom tells me my airtime will fall away and I cant transfer it to another Vodacom number I have as it is their policy. So in other words their police is to ***** my airtime which I have paid for over the last two years????? I will not accept this and I demand my airtime to be transferred to another number. I don't care about their policy allowing them to ***** from me as I paid for this airtime.