Vodacom Airtime @ Food *****s Westgate

I bought Vodacom Airtime at @ Food *****s Westgate on the 27th March at 15:54 I tried to load it the same time I bought I received an error that the voucher is been used. I flag the problem same time in store then the manager told they can't help me she can't do nothing about it which I have lost R55 just like that. I don't believe I got no assistance, she promised to call me back up to now. I bought airtime for the reason to use it at that time.