Send SMS to
121 SIM (you new sim number here)
which is a 20 digit number
If it's successful you will get a SMS like this
Dear Customer, we have received your request for SIM change on airtel mobile. Please do not proceed if you DON'T HAVE A NEW AIRTEL SIM with you. For your account security and to avoid any banking or financial fraud, SMS services will not work on your mobile for next 24 hrs. To confirm for SIM change, reply with 1.
Now reply with 1
You will get a SMS like this now just put the new sim in and wait for it to get activated
Thank you! New SIM will be activated shortly for your Airtel Mobile. Your old SIM will work till the new SIM gets activated. For security reasons, SMS service will remain blocked for next 24hrs.
Sometimes you might get an error like this
Wrong HLR GOLD SIM, Please try again with Correct HLR sim number.
This is because you either did an MNP mobile number portability to Airtel or in my case changed automatically to Airtel because Aircel stopped service in my area.
In this case to switch to Airtel 4G you need another sim. Check on the sim pack see it says H 1 or H 2 sim.
If it's H 1 get the H 2 sim and follow the above mentioned procedure and it should work
Now enjoy Airtel 4G speeds and new sim on the same number