Go on small cunning and try to find the data about the subscriber from the operator of cellular communication. The fact is that when you Deposit money into the room, visible to the operator of the personal data of the subscriber. Knowing this fact, you can pretend that you came to pay for the phone of your girlfriend or friend or second cousin of the grandmother of your mother in law or who think of themselves, but the last figure I forgot. She invented a person can not come, because is in the hospital. Make pleading eyes (preferably like a cat in the movie "Shrek") and ask for help, because the operator can call you not only name, but also surname, first name and even the address of the residence of the subscriber. Good bluff, in order not to give itself, and the operator can see through you and won't say anything.
All mobile operators have a database of its subscribers with their phone numbers and other information you used when buying the SIM card. Try to get access to this information, searching such database for sale on makeshift wheels. Can also apply to law enforcement agencies, entitled to receive such information through official channels. Better, of course, if you have a personal acquaintance with a person of access to information of this nature, because otherwise, you will need good arguments in order to make a formal request.
Try to enter the number in numerous sites on search engines that hit the Internet. The sites have both paid and free, but for the quality of the information provided, as you know, no one is responsible. But this option is its simplicity and accessibility.
Try to drive the number of the desired person in different search engines are popular social networks. You might be lucky to find his page, but remember that access is not always open to outsiders.