MNP is a technology that enables a mobile phone user to switch to a different mobile operator without changing his original number.
For example, you own a number of BSNL and you feel you need to change your mobile number, you can simply request any other operator like Airtel to give you the same number in Airtel. This technology, however, is not yet implemented but soon, it will be launched countrywide as per the government's discretion.
You can know about phone number portability via https://toughnumbers.com/.
How does it work?
MNP will be implemented based on a code called "Local Routing Number" or simply, LRN. An LRN is a 4 digit code and it will be responsible for all the call routing after implementation of number portability. Post MNP launch, all mobile will be identified by 4 digits additional number + 10 digit original number. This way a phone number will no longer remain a ten-digit number for an operator.
So, does this mean one will have to update his phone book number with a weird 14 digits mobile number later on? Of course not.
These changes will be done at the Service provider level and for a common user, his number will never change. Obviously, MNP does not make any sense if everyone has to change his phone book after its implementation.
common user may experience some initial trouble once its number is ported, but later on, he can enjoy all the facilities by another operator he is going to switch to. As per TRAI (Telecom Regulatory Authority ), you can not request a change for your number again for at least 3 months after you make a switch.
So, once mobile number portability is launched, make a careful decision to choose a service provider to avoid any problems