iPhone X requires activation after update to iOS 14.3

My sister just gifted me her iPhone X she's been using, which was bought new, factory unlocked and she have been using a local (Nigeria) SIMs on it.

Before I start using the phone I decided to back it up with iTunes, erase it, update it to the latest iOS version and then restore my backup from my previous iPhone 6s+, all I did successfully but didn't insert a SIM.

After the update was complete I decided to insert my SIM and I got the Activation Required popup and then the SIM Not Valid screen.

Am so confused I don't know what to do and I can't seem to find a way to contact Apple from Nigeria.