How do I know which network my device is locked to?

Dennisco300 wrote:

if my carrier provider is not in my region, how or who do I reach out to unlock my network carrier???

Contact the seller and request they resolve this, or return this iPhone for a refund.

Otherwise, you bought a brick.

The Related Article linked above describes how to determine if the device is unlocked.

Since this iPhone is carrier-locked, and which carrier is not clear from the Settings > About and > Cellular displays…

You can ask Apple to which carrier: Contact Apple for support and service - Apple Support

Various carriers will either not unlock at all, or will not unlock for third-party unlock requests.

And only the carrier can unlock.

Which carrier are you paying every month right now for service?

Whoever that may be, you will need to contact them if you want them to remove the carrier lock on your phone.

Only the carrier can remove the lock. Apple cannot help with this in any way.