I tried that with Halifax, they weren't interested unless I could show with a receipt that I had been overcharged, and of course you get no receipt on a tap and pay machine.
If that were me, I'd leave Halifax.
They are obliged to respond to any transaction query and put it on hold. The receipt is irrelevant, they have the transaction information and far more than you see on your card statement.
Sorry to hear they dealt with you so wrongly. You could write a formal complaint.
Other card providers should be far more professional than that.