Mobile number portability (MNP) enables mobile telephone users to retain their mobile telephone numbers when changing from one mobile network operator to another.
As a mobile phone user, you have numerous choices to choose your prefered Mobile operator. Almost most of us having mobile phone, on some time you may inclined to switch over to your prefered mobile operator, but without changing your mobile number. If this is your position, you can go for Mobile Number Portability (MNP).
From your existing mobile number send te following SMS . PORT <space> <10digit_mobile_no> to 1900. Example : PORT 9123456789 to 1900 and you will receive a UPC(Unique Porting Code) CODE in reply SMS. Note it down. The UPC is valid for 15 days (30 days in case of J&K, NE & Assam Service Areas).
Now goto the nearest Customer service centre or the retailer of the operator you want to shift to and fill an application form, with the UPC code received by SMS. Also you need to provide a copy of valid address and identity proof and submit a passport size photograph as well as. They will give you a tentative date of your mobile number will functional in new mobile service provider. And you will also get a new SIM card from them.
The customer centre will give a empty sim, after your payment and document submission. With in 1 day you will receive an acceptance message to confirm the porting.
Once your mobile number ported into your prefered new mobile operator, your old SIM card stops functional. Now its time to replace your old SIM by new SIM. So nsert the new sim in your phone, Now you are in the new network with old number. And your choosen new Mobile operator service starts functional.