Of course I've made mistakes, Doggie. I just don't consistently make them, then when caught in what appears to be another example of my inherent dishonesty, I don't say, "Oops, I simply made a mistake".
You operate a lot like a grocery store I no longer frequent. They rarely had the price that was programmed into the cash register the same as the lower price advertized on the shelf or the weekly flyer. I got so tired of the lame excuse that they simply made a mistake and charged me more when they always made that same 'mistake'.
It's a trust thing. Folks who know the value of being trusted make sure they have integrity and keep it.