I sent my chap out to clean the reception areas and a few staircases for a well known hotel chain. They had not contacted us or requested work, we just did it.

The manager approached my cleaner to find out what was happening, my guy told him he was cleaning the carpets. "Fair enough" said the manager as he walked passed.
We invoiced head office and the cheque came this morning (1 month later).

I would not recommend this method though.
I just wanted to prove to myself how bad communications are with large companies.
Matt