When you receive calls from a number you do not recognise or come across numbers you have written down but don't remember who they belong to, you can find out who owns that number. Available via the Internet, this process is referred to as reverse phone lookup. Using reverse phone lookup is free on many sites and will provide you with names and addresses associated with the number. Other information is available, but normally requires a fee.
Use an Internet search engine and type in "reverse phone lookup" to search for appropriate sites. Switchboard.com and Google are two popular resources.
Go to the search field labelled "reverse phone" and type in the number. Some sites require the numbers be separated by hyphens (e.g. 972-555-1212). Hit enter and you should see the owner's name. Depending on the website, you may also see an associated address.
Search for a cell phone number using an online mobile phone book. Go to the reverse search field and type in the number. You may be charged a fee to research a cell phone number since they are bound by agreements with various phone companies and fall under the Wireless 411 Privacy Act.
Use an up-to-date database.
Mobile numbers are constantly changing, so you may get a former owner's information.