I'm going to try the 100% money back guarantee, If you get a minger and the customer has unrealistic expectations on the results then, you walk away.
Years ago i had a customer who wanted her money back saying there was a stain that had not come out, I went back out to have a look, she wasn't in, daughter let me in, could not find a stain. customer phoned again ranting and raving that night for her money back. Went out again could not find the stain. Daughter then draws the curtains and put the light on And there was a faint stain, Trust me it wasn't there when i left, but no problem just a quick spot clean. Only the daughter said her Mother instructed her not to let me clean it. and to just get the money off me. Told the daughter would not be refunding any money, walked out.
Customer phoned in the evening, again demanding money back, told her I've offered to clean the stain, and that was as far as i was going. Advised her to phone trading standards. never heard from her again.
In 32 years I've only ever given 1 refund, for a re stretch and the fitter told me it wasn't my fault she had cable fitted after the clean, and they pulled the carpet up. She didn't tell me that. I thought I'd shrunk it, when i went out to see it.
Remember if a customer is not happy, you have the right to re do the work. first.
Alby