I've only received two of those types of calls. First one just left a short message ranting giving their name & address but no callback number.
The second call just wanted to cancel because its been taking to long for the work to get started...not me. Apparently the guy was holding up another company's job quote on their fridge with one of my magnet business cards.
After explaining to the guy that I wasn't the one who he hired, he ended up giving me the job and I had it done the following weekend, ...at my price of course!!!
HC