The Nextel Communications Company was a cell phone service provider that went defunct in 2005 when Sprint acquired the company and founded Sprint Nextel. Many people still have Nextel phone numbers from that era and even more are registered with Sprint Nextel. Finding a Nextel cell phone number for free requires using a free cell phone directory online. As long as you know the person's name, you should be able to search for their Nextel cell phone number.
Find a cell phone directory (see References).
Search for the person whose Nextel number you are trying to find. Enter his name in the Search field. Depending on the directory you are using, you can also do a search for a particular region.
Analyze the search results. If there is more than one result, call all the numbers until you have found the one you are looking for. If you don't get a cell number listed from a search on one website, try another one.