I had an older listing that gave a $13 charge for shipping a book within Canada by Regular Parcel.
A new customer bought it and paid immediately.
Good.
When I was packing it, I realized I could send it Letter rate, so I refunded him $10 and sent a note to that effect.
Since when I have received 3 emails asking why I was not going to sell him the book (response- you are getting the book, but I reduced the shipping charge) why he wasn't getting Free Shipping (response, - the book is being sent First Class- not an actual answer, I know) and whether he had to buy a different book (no- you paid for this one, you're just getting it cheaper than you thought you would.)
Sigh.
😛