Dial 123 from your BSNL SIM and follow the IVR instructions
Dial 1503 from your BSNL number and ask customer care for your mobile number
Dial 199 and request your BSNL number details
Check your SIM pack, bill, or activation documents if available
Call or message another phone number from your BSNL SIM and note the displayed number
Check your phone settings under SIM or About Phone to view the number
Use the BSNL Selfcare app if your number is already registered
Visit the nearest BSNL customer service center with valid ID proof