Check your phone’s Settings app
On iPhone, go to Settings > Phone > My Number
On Android, go to Settings > About phone > Status > SIM status
Open the Phone app and look under Contacts or My Card
Call or text another phone and see the number displayed
Dial your carrier’s self-service code
Check your SIM card packaging or account documents
Log in to your mobile carrier app or website
Ask a friend or family member to read the number from their caller ID
Contact your mobile carrier support