BP PETROL VOUCHER ****

I purchased a BP petrol voucher for R440-00 and tried to redeem it at my usual petrol station at Southfield and each time I went there it was declined. I called BP support and they told me that the voucher was redeemed at BP Tokai. I told them I never fill up at BP Tokai and asked how it was possible for the voucher to be redeemed while it was in my possession and was told they could not explain this. I am now out of pocket of R400-00 which I paid for the voucher and trying to find out how it may be recovered.