We had another today.  I cleaned a house last month and it was utterly filthy.  We did a good job.
So we turned up to do it this month and there's a note saying:
'Attention Window Cleaner
Please do me every other month'.
Now this lady had been given my card and we agreed a monthly price.  So I was fuming.  I knocked the door and her husband appeared.
He was a big bloke, and my missis had started cleaning the house next door; but watching us.  I must admit I was cross and not very tactful.  
He said he hadn't had a window cleaner for 12 years and his wife shouldn't have got one without him saying first, then he aggresively told me to 'stop giving him attitude' .
I saw red and I'm ashamed to say I nearly did a 'Gazza' (Sorry Gazza).  I slung my ladders with a loud crash onto his lawn, stepped closer to him and gave him a peice of my mind, along the lines of, 'Isn't your missis allowed to think for herself?  Did you not have the decency to phone me?  I know you didn't have a window cleaner for 12 years - I flipping cleaned them last month.  
He obviously saw I was raging mad Geordie, so apologised in the end, saying 'Sorry you feel that way' and blamed his wife.
It really spoilt my day.  Wor Lass gave me a telling off too for acting like a yob and throwing the ladders down.  But in my defence, he was a lot bigger than me, so I had to act a little 'crazy' to give me the edge.
But, what makes me cross is, I lay out my stall and they ask to purchase.  Then when they agree; the blighters try and change the terms and conditions on you.
AAAArrrrggggg - The next one had better watch out!!!!!