How to Trace Any Mobile Number?
Well, there are several ways to do this.
 The easiest way to gain access to the details of any mobile number is 
by using a reliable paid service that has records of over millions of 
mobile and landline users in its database. If you’re really serious to 
find out the name and address of the person behind the mobile number, 
then this is the right choice. You can use the following service to get 
the details of any phone number (mobile and landline):
Cell Phone Registry – Trace Any Mobile Number
Please note that the above service works only for the “United States” telephone numbers.
Other Possible Ways to Trace a Mobile Number:
Now let us look at some of the free 
options that are available. Even though it is not possible to trace the 
number back to the caller using the free services, it is possible to 
trace it to the location of the caller and also find the network 
operator. Just have a look at this page on tracing Indian mobile numbers
 from Wikipedia. Using the information provided on this page, it is 
possible to certainly trace any mobile number from India and find out 
the location (state/city) and network operator (mobile operator) of the 
caller.
All you need for this is only the first 
4-digit of the mobile number. In this Wiki page you will find all the 
mobile number series listed in a nice tabular column where they are 
categorized based on mobile operator and the zone (state/city). This 
Wiki page is updated regularly so as to provide up-to-date information 
on newly added mobile number series and operators. I have used this page
 many a time and have never been disappointed.
If you would like to use a simpler 
interface where in you can just enter the target mobile number and trace
 the desired details, you can try this link from Numbering Plans. With this, you can trace any number in the world.
UPDATE:
 After the introduction of Mobile Number Portability (MNP) in India, 
methods discussed above are not found to be very much accurate.
By using the above free services, you 
can only know “where” the call is from and not “who” the caller is. Only
 the mobile operator is able to tell you ”who” the caller 
is. Unfortunately in India, there is no such paid service that gives you
 more accurate details about the caller. So, if you are in an emergency 
and need to find out the actual person behind the call, I would 
recommend that you file a complaint and take the help of the police. I 
hope this information has helped you!
