One of the most annoying aspects of having a beautiful wife or girlfriend is that other guys are inevitably going to try to talk to them.
They'll have no respect for the fact that you're the person it's with him, and may even try to make themselves look like a better man than you to try to steal away your woman.
Don't take it personally; it happens to everyone at some point or another in their lives.
The point is that if these types of interactions are going on with your wife or girlfriend over the phone, you deserve to know who the rat behind it actually is.
Whether you realize it or not, the means by which you can accomplish this already exists in the form of reverse phone lookup services.
It's not that you don't trust the woman that you are with to be faithful to you, what is reasonable enough for you to want guys that may be harassing her to leave her alone.
It should be trivial enough for you to be able to track down the phone number of the person that has called and spoken to your spouse.
If your woman does not have their contact information saved, then that's probably a good sign, especially if you're concerned about her fidelity.
On the other hand, she might just be trying to hide the guy's name from you.
The next step is to go to a reverse phone lookup service, and use it to get the name or address of the guy whose phone number you managed to recover.
Once you've managed to locate a site that looks like he can do the job, the process of actually conducting the reverse lookup on the cell phone number is fairly straightforward.
In a matter of minutes you can have the information that you're after, and the guy who has seen fit to violate your territory as a man will be very surprised when you are not only able to get in touch with him, but able to refer to him by name and your conversation.
That's a fairly intimidating combination! Hopefully he'll take the hint and move on from there.