...were not about whether the windows were clean or not, ... the said that they didn't like how their windows were cleaned.
Well then I'd drop them, as I have one (now ex) customer of mine.
Your customers pays for clean windows, which is what we provide.
They don't pay us (or me rather, as Wor Lass rarely climbs a ladder) to see me sweating or risking a fall.
If clean windows and frames aren't enough for them; dump 'em.
One of my customers recently joked that my new system looked 'too lazy'.
You just know that a tiny minority of your more negative-minded customers will get upset that you're earning X-amount of cash in Y-amount of time (Y = a short amount of time); and you're not even risking your kneck to get it.
No wonder some of them get upset.
When I first started window cleaning and 'flyered everywhere', I had a nurse phone me and ask for a quote. She'd obviously had a drink too.
She was upset that her window cleaner had just put up his prices, again, and told me that it just 'wasn't on'.
'Come on', she said, 'You guys must be earning a fortune, and there's me getting abuse and violence every weekend in accident and emergency; for a pittance'.
I told her that if she was so unhappy with her 'dangerous' occupation, she should become a window cleaner.