Many people carry two SIM cards: one for daily use and one for a work number, a family number or better coverage. The second one usually needs very little.
Step 1: Decide what the second SIM does
If it only receives calls and a few messages, you do not need data on it.
Step 2: Use a voice-only plan
The new voice-only plans fit this use well. Airtel’s ₹185 plan lasts 28 days and Jio’s ₹177 plan lasts 28 days, with unlimited calls and 300 SMS and no data. For a longer break between recharges, Jio’s ₹448 plan covers 84 days.
Step 3: Note the expiry date
Set a reminder a few days before the plan ends. The rules for how long a number stays active after validity ends differ by operator, so check yours in the app.
Step 4: Use Wi-Fi for data
Messaging apps and email work on Wi-Fi, so you rarely need mobile data on a backup SIM.
One caution
Some services, including banking alerts and one-time passwords, may arrive by SMS to a number you registered. If that number is your second SIM, make sure the plan includes SMS and stays active.