I'm self employed and have had the same business number for 25 years now. So, I'm on just about every call list you can imagine. The rudest, most annoying calls I get are from the "Wall Street" brokerage firms that want me to switch all of my investments over to them. I generally just say "not interested, please take me off your call list" and I'm amazed at how often they either argue with me or curse at me when hanging up.
I also get countless calls to A) move my office, B) re-roof my building, C) buy all kinds of office supplies... toner, paper, etc. D) change my "merchant account" for lower rates on the credit cards I accept (which is none) and D) professional education services.
The calls are generally heaviest on T,W,Th. Monday's and Friday's are generally fairly quiet.
When people call and say they want to talk to whoever is in charge of ____________, I generally tell them that all of those decisions are made by our parent company office in Shang-Hei. I've only ever had one guy actually question that.
I will also tell the people wanting to talk to whoever is in charge of our electric / gas / etc. bill that we don't use electricity, gas, etc.