I used visa paywave to pay for my groceries the other day -- waved the card over the terminal , it beeped, all good. 

But, the checkout operator said it didn't go through rescanned and made me use paywave again, another beep. 

But, I told her I thought I'd paid twice so she got her manager who sided with the operator and told me to return with my receipt and credit card statement.......I would have thought they'd have given me the benefit of the doubt for a $10.00 transaction. They spent 15 minutes trying to figure out what happened too. 

So, today, I see I've been billed twice.

Anyway, the point is, that some staff have not been trained on how to use paywave at supermarkets, so , might not be the best idea to use it.