Lost TFG Rewards voucher

This is the second time that I had an issue with TFG Rewards. I've been a loyal customer for more than 10 years and had really poor experiences the last 2 times that TFG had given me a reward vouchers which I take to the store to use and before purchasing I ask the consultant if I can use it for this purchase. They use it and mess up the pricing and when I request a refund they say Sorry you lose the voucher.

you've been rewarded with R150 off. Use MTH078XF73JQVY7 at TFG or any TFG store until 19Nov.

Most recent voucher used at Foschini in Gateway. I asked the cashier if this voucher would work on my purchase of goods that are currently on promo. I was advised that I could use the voucher. I did. After payment I realized that the i store promo did not apply to the sale. I went to rectify this as I was advised that I would still receive the store promo with the purchase if I used the voucher.

The manager then says that I won't get the voucher back and there is nothing that can be done. This is the 2nd time I had lost a voucher due to wrong information given to me at the till points.

Please can someone assist with re issuing this?