I saved a customer £2k a few months ago!
As Team Leader, Petrol, at a major supermarket, I was approached one night by a customer seeking help. His Audi had been misfiring, the garage claimed it was dirty injectors caused by 'contaminated cheap diesel' and therefore the fault and necessary repair work wasn't covered by his warranty. He'd have to pay.
I said that we take claims of fuel quality very seriously, and would immediately look into it.
He didn't have his receipt, but I found his car being filled on CCTV, so I could identify the time and pump (and tank) that was being used. I printed off his transaction, and then checked when that tank's diesel had been delivered. A few sums later, it turned out that he was the 170th customer using that fuel, and he was followed by 30 more before the tank was refilled. No one else had submitted a complaint, and the delivery paperwork showed no obvious contamination at the time of delivery.
I wrote these details down in a brief letter, which the customer picked up the following day.
A month later, I was tapped on the back while in the store.
It was the customer. Absolutely delighted. On seeing the evidence, he said, the garage did the work for nothing.
Result!