Being investigated by rivals in business over the phone without your knowledge is a more common scenario than you might actually think.
Often times, people who are working in direct competition with you and your small business will try to call you in order to test out your customer service, and find out information about how you conduct business by posing as a customer.
Often, this is done so that they can adjust themselves to better compete with you, and you don't want that.
Staying on top of who's calling you is a lot easier when you're using a reverse phone lookup service to keep track of received calls.
It's true that a lot of potential customers they call your business are average people who might have the numbers blocked for their own personal purposes, but that can also be a telltale sign of another business who is scouting you out.
If you're starting to get suspicious, and you happen to have quick access to the Internet, all you have to do is plug in the phone number of the person that's calling.
Even free reverse phone lookup services should be able to give you details about the phone number, especially if it belongs to a brick-and-mortar business like your own.
If it's a cell phone that's calling you, you might have to refer to a higher level online phone directory, which might charge you a small fee for the service.
This is less likely, however.
The more probable scenario is the other business using some sort of crude masking service to try to block the name attached to their number, and just calling you from one of their land lines.
Using reverse phone lookup, you can beat them to the punch quite easily.