TRAI has made it easier, and faster, to switch phone number from one telecom operator to another. So, if you are planning to switch from Airtel to Jio, or vice-versa, without giving up your existing number, it will take no more than two days to get on to another network.
Telecom Regulatory Authority of India (TRAI) issued seventh amendment to the Mobile Number Portability (MNP) regulations, citing a major shift in the mechanism for generating Unique Porting Code (UPC)
Right now, after you send the request to port your number through SMS, a Unique Porting Code (UPC) is generated. You need to apply to the operator you need to switch to within a stipulated period of time.
Then, new operator takes permission from the old operator and communicates this to MNP Service Provider (MNPSP, that serves as link between your old and new operator). Then old operator withdraws services, passes the message to MNPSP. The new operator can now claim the number and activate services on the new number.
This process usually takes about 7 working days, the time before you get the new activated SIM, Now it will take two days.