Not to be negative, but i can't think any proper business wouldn't have a window cleaner.
You'll be taking a contract from someone else, for sure.
But this isn't necessarily a bad thing.
It could be price. It could be service. It could be your attitude.
If you're better, you may get the job.
Just because a company has a window cleaner, doesn't mean they're happy with them.
My residential stuff is always getting canvassed.
My commercial, less so, but it does get canvassed.
Sometimes losing a job can be a good thing too. One may have been getting complacent.
Canvassing only 'good' leads just can't be done imo. There will always be some dross in with the gold. It's sorting that out that will make one's business.