The Supreme Court however has given four-months for these operators to continue their services. So if you want to shift to other operators without changing your number, you can opt for Mobile Number Portability or MNP.
Here's how MNP works.
To begin with, you need to generate UPC (Unique Porting Code) by sending SMS to 1900. UPC is an alphanumeric code allocated, upon request, by a mobile operator to its subscriber for the purpose of facilitation of porting of his/her mobile number to another operator.
You just need to SMS "PORT"
But, before applying subscriber needs to keep in mind while porting are that porting is allowed after 90 days either from the day when an existing number was activated, or from the time when it was last ported.
After sending SMS to 1900, you will receive UPC (Unique Porting Code) through an SMS from 1901. The SMS will have an 8 digit alpha-numeric Unique Porting Code and will have a validity of seven days.
You have to visit the nearest showroom/outlet of your desired operator where you need to fill up the MNP form and submit address and ID proof documents, a self-attested photo and the mobile phone bill of previous month if you are a post paid user.you will be charged a porting fee of Rs 19.
Remember that the UPC has seven days expiry date after which it will have no use. So if for some reason you cannot change your operator within that time, you have to apply again by following above mentioned procedure again.
Your operator will then check your application for MNP and if you do not have any dues left, it will grant approval for porting. According to TRAI's guideline, your telecom operator has to grant its approval if the dues are less than Rs 10.
You will then receive an SMS from your new operator on the time and date when the porting will be taking place.
There will be a 2 hours' no service period after the porting time that was mentioned on the SMS. After that you can change your old SIM with your new operator's SIM card. Do note that here your number will be the same.