I once bought a brand new tv in Tesco. My old one had died and I'd decided to take advantage of a new credit card deal of 0% interest, plus - Club card points.
So I went, chose, took to the til and paid with my new card .
The cashier made an error and put the transaction through twice. So she deleted the transactions and put it through as a fresh sale.
My receipt in hand, I left the store.
A month later my credit card bill arrived and it had a zero balance. I was really confused.
Checked my receipt.
She'd firstly put through the correct amount, £400, but must have thought she'd done it twice...only she hadn't. She then deleted the "correct" amount taking the balance on my card to 0, and deleted again taking it to -£400, before starting afresh and putting the £400 on, taking my credit card balance back to 0.
The credit card company (Tesco Bank) actually laughed at my honesty and said that as it was over a month, there was nothing could be done. The store weren't interested either.
I paid for it ultimately as that credit card spiralled out of control, lost my job through illness and ended up with a CCJ.
So not really a free Tele after all ;)