Coupons NOT scanning correctly

For the 3rd time I have been humiliated at the cash register when trying to access my printed coupons from the website!!! This is seriously frustrating as it takes over and hour to realise that my query cannot be sorted out. My picture printed email for coupon code *** was valid for a discount of R101.00 but at the register it was only showing R71.00. I don't know what else to do??? I had to leave ALL my items behind because they could not validate the coupon. I am almost too embarrassed to return to that store as I now look like the fool with the coupons that dont exist!<br> CAN SOMEONE PLEASE SORT THIS OUT AS A MATTER OF URGENCY???