Vodacom stole my airtime.

I requested an online upgrade on Vodacom website on 07 November 2018, a consultant called me soon after to process the upgrade. I specifically asked about my existing airtime balance, as it was substantial (approx R1700), and I was assured that it will not be lost as the contract type stayed the same: uChoose Flexi 350 to uChoose Flexi 220. On 01 December 2018 (new contract due date) I checked on the Vodacom app that I am on the correct contract and my airtime balance and all was still there, so I was happy. Checked my airtime balance today and and all the previous airtime is gone, NOT HAPPY. I called 082135 and after speaking to 3 different consultants the issue is still not resolved. Vodacom must repay the money! Spoke to several Vodacom shop employees and managers and all agree that the airtime should still be available.