Dial 123 from your BSNL mobile and follow the IVR prompts
Dial *123# and check the displayed balance/validity details
Use the BSNL Selfcare app to view plan validity
Log in to the BSNL website and check your account details
Send an SMS as per BSNL’s latest validity-check format in your circle
Visit a BSNL customer care center and ask for validity details
Call BSNL customer care at 1503 or 1800-180-1503 and verify validity
Check the recharge confirmation SMS for plan validity end date