It's simple. Setup SIM lock on the SIM you use for your bank transactions.
When your phone gets stolen and your phone is locked with a password or pattern, the thief will be forced to put the SIM in another phone or wipe the phone. If SIM lock is set up, he won't be able to gain access to your contacts and BVN.

When a thief steals a phone, the first thing he does is switch it off or/and remove the SIM before using it for malicious act, So in that process the SIM lock is activated. But it's better to use a pattern/password too for full protection.

To set up SIM lock, Go to Settings >> Security >> Set up SIM card lock

Nice info

Incase of emergency nko?

begwong:
Incase of emergency nko?

Which emergency? I don't get you. Please explain better