So if you've managed to salvage the mystery number from either your call-display or your partner's caller history, here's how to find out who's been calling...

1. Use the Reverse Phone Directory on WhitePages.com and AnyWho.com

That's a fairly self explanatory step, but make sure that you run the search with and without the area code (if no results come up at first).

This method will pull up any registered, listed residential and business numbers.

2. Use Search Engines Like Google, Yahoo and MSN to Find Owner Information On Cellular, Unlisted, 1-800, and Pager Numbers.

In very basic terms, simply head over to Google.com, type in the phone number into the search box, and press search.

Use the following formats when entering the phone number...

"111-222-3333"

"1112223333"

"222-3333"

"2223333"

And so on. It's important to include the quotation marks around the phone number so as to only include results that include that actual number, rather than fragments of it.

If you don't have any luck with Google, make sure to repeat the process on MSN.com and Yahoo.com, as each of these search engines has unique and varied results - and reach.

3. Place an Official Lookup Investigation Through a Reputable Online Service.

As you've probably already discovered, cellular numbers, unlisted numbers, some business numbers and pager numbers are not listed in any public directories - and if they are, those directories will either be partial, outdated or both.

You'll need to place an actual trace using an investigative firm or service. This will run you about $35 - $99 or so for anything that actually lives up to its claims (you get what you pay for).

Services abound - just make sure that they offer a guarantee (refund policy) in the event that they can't find results on your number.

Some even offer a sample/partial search, so you can see if they have the number in their index or not before placing an order.

Better yet - find a service that offers both a sample search AND a reasonable guarantee or refund policy.

And, before you begin to worry - yes, it's legal for you to place a search on someone else's phone number if they've been calling you. And due to the nature of the internet, it's also discreet in most cases.

That's how to find out who's been calling you, or someone you love.

Happy searching!