This has been happening a lot to me this spring. I go out to cut a customer's lawn, and when I'm done they ask if I could do some other quickie service for them (prune something, put down some bags of mulch, spray some roundup, etc.). Then they give me some $$$ and say "that's for cutting the grass today, and I included extra for the other service" I look down and see $3 "extra" dollars! I am like, HELLOOO, do I have a paperboy sack over my shoulder? I politely give them the "extra" money back, and inform them that I can accomplish the additional service request for XXX dollars. They usually act shocked and say "that's ok, I'll get my so in so to do it". Jeez, some people never stop trying to get one past you!