If you want to port your current mobile number to other network. Then sms PORT <your mobile number> to 1900.
After the text you will receive unique porting code as sms from 1901.
Go to the store of mobile service provider to which you want to switch.
Fill the mobile portability form with the unique porting code and submit your address proof.
You will have to buy a new sim card at the same store.
Within two days you will be ported to another network.