Vodacom accounts cancellation/switching to prepaid

So I phoned in to have a a flexi top-up account (already out of the 24 months period) cancelled/switched to pre-paid. Didnt realise that there was still R76 airtime left expiring end of Feb 2020 and still R210 airtime left expiring end of March 2020. Vodacom now claims that i will loose all airtime when chainging to prepaid? How is this possible? I already paid for the airtime. Will still be using the same sim, with same nr in the same phone, simply moving the account to prepaid in order to lessen accounts. When asked to speak to one of the supervisors or managers in the call centre, I was simply put on hold, been going on for 15 minutes already, no background music or nothing to indicate call was still ongoing? Pathetic!!!!!