There are reverse cell phone directories you can use to track down these people just by using their cell number. There are many many sites on the web that do offer free reverse phone look ups, but these only cater to landline phones.
Cell phone search is not available on such free directories, and it is quite understandable why; cellular phone information doesn't fall under the public domain and simply can't be revealed easily. Until a few years back, the only option was a detective but then why pay a detective so much for finding a name? Your home number is considered public domain information and has been for decades.
Suppose you know the phone number and surname, but you need an address, you can easily trace a name from a phone number and last name, and it will also give you the first name. This is because landline numbers are easy to collect and organize since they are public domain property. For instance, that ex lover could want to re unite, but is too embarrassed to leave a message.
If you do not get results, you can get refunded by the reverse cell phone lookup service. You can also go to sites like this one to get reverse information on a phone number.