Switch to a nation carrier like Airtel, BSNL, Tata docomo etc. Don't go with local carriers who are shutting down their networks in many areas without even informing the customers.
So switch to one of the big mobile providers while you can using MNP.
I had to go through this recently when Aircel stopped service in my area without notice. I went for two week without mobile while i switched to Airtel network. All the while fearing my phone number would not be lost, luckily i was able to get the same number.
Because all the 2G scam and 3G auction issues courts are asking many smaller networks to shut down in certain area etc. Liks this Uninor to close telecom operations in Mumbai from midnight. So switch to big national providers as soon as you can if you don't want to lose you number.
Here is the MNP procedures
To shift your mobile number from one operator to another, a customer shall send
PORT <your Mobile Number> to 1900.
You will receive a unique alphanumeric UPC (Unique Porting Code)as a SMS from 1901 giving 8 digit alpha-numeric Unique Porting Code (UPC) and UPC expiry date in MM/DD/YYYY format.
Visit the office of your new mobile operator and give them this UPC Code.
The customer should have completed a period of 90 days (from the date of activation of the mobile connection) with the current operator, to be eligible for porting to another operator.
Do do it and switch now before its too late.