Remember if you upgrade, then it is actually benefitting the mobile operator since 4G internet costs less for them.

SIM Cost

If you go to retailer then he may give you new 4G SIM for free. Depending on city they may charge you Rs. 20. But if you go to company official showroom then it will be free for you. No cost needs to be paid and no mobile money will be deducted

What you need to Carry

3G SIM which you want to upgrade. No need to carry any ID proofs.

How much time it takes

It usually takes around 2 hours but depending on conditions it can take 1-8 hours.

Steps

1. First go to any retailer with your mobile phone with the 3G SIM
2. He/she will give you a new 4G SIM and do a SMS which is different for every mobile operator. For example for Vodafone here is the SMS:

   SIMEX [4G-SIM-Serial]

3. Then you will soon get a confirmation SMS and an option to cancel it. If you choose then you can cancel this upgrade. For example for IDEA 4G upgrade it will ask you to reply 'Y' else your upgrade request will not succeed.
4. You will get one-two more SMS from the mobile operator whether your upgrade has been accepted or not and what to do next. Just keep reading them.
5. Watch out your mobile for SIM signal. As soon as it disappears replace with new 4G SIM. In case of any problem, restart your mobile