I used to manage administration for a reasonably large online business.

We had a 14 day money-back guarantee – always.

Someone once called up wanting to return a product – it was around the 25 day mark. I politely explained we had 14 DAY guarantee – he swore I was wrong, and it was a 30-day guarantee.

I politely offered to accept if I was wrong – if he could show me where it said 30 days.

He told me in a letter that came with the parcel.

I said it shouldn’t have, and that the letter that is included in the parcel just thanks people for their purchase (read: politely suggested he’s a dirty great big liar ) – but I would honour any commitments we made.

A few days later, I received a parcel from him. It included the thank-you letter with a bit tacked on to the end – it was printed in Inkjet Printer ink (we only used Laser Printers) and read “Please Note Our 30 Day Guarantee Period”.

Leaves you in an interesting situation..

Do you spend more time arguing? (costing yourself more money in time)
Do you send the parcel back? (costing you postage)
Do you tell the customer to ship it back at their cost? (Which they probably won’t do, and will waste your time arguing over)
Do you just refund the parcel and be done with it?

Sooner or later your time is better (more profitably) spent on other tasks. I refunded the parcel, and was done with it.
I resold it the next day and made back the full refund amount.

Most people were honest though.