Perhaps your BSNL SIM validity has entered GP1 or Grace Period 1. Mention all the details except your actual mobile number.
Alternatively, the best way could be to approach BSNL office or BSNL Self-Care app.
There's a 107 Plan that offers 30 Days validity.
However, MANY would want to know the cheapest way to keep a BSNL SIM active without Calls... ONY Incoming and SMS in 2024 (September).