I have managed a major retail store for 19 years. It is a smaller national retailer with an intimate, relationship building approach to sales. In that time, even though I run a pretty tight ship, mistakes have happened like this.
Number of times they were intentional? ZERO. Number of times I got up in the morning and thought to myself, "Self, how can we screw people today for our own personal gain"? ZERO. Number of times we get accused of lying and intentionally trying to screw people? Almost every time any mistake happens. And even at times where nothing at all went wrong in the interaction. And every time I think to myself "I hope to catch you in an alley behind a bar one night".
The thing I have always hated about sales is having the stigma of stereotypical salespeople. I live in a relatively small community, and a bad reputation will sink you. You get accused of lying often enough because people have this weird mistrust of any retail business without actually giving them a reason to.
Sounds like a mistake happened. Sounds like they made it right. Accusing a person of dishonesty without hard proof and when there is doubt is an awfully bold step. However when given the freedom of the internet and the anonymity it brings, it happens more and more which only fuels people's mistrust.
There are dishonest retailers out there I am sure. But assuming everyone is like that is like saying every person that owns a gun is a criminal because criminals often have guns.
But one thing I can tell you. If a customer returns to my store after a mistake has happened with them, and they handled it with grace, the service seems to step up an extra notch for them going forwards.
I am not saying the OP was accusing anyone of anything. Just a thought...