Seems like that device may have been configured for a certain carrier. If you have the box, see if the model number is listed there. That should allow for identifying where the device was intended to be sold. While you purchased it at a local reseller, are they an Authorized Apple reseller? It could very well be a gray market device, which could cause you problems. The warranty for the device begins at the time of sale, which would differ from when you purchased it.
TNT is a cellular service provider in the Philippines.
iPhones in many regions around the word come with carrier sim cards pre-installed.This is not at all strange. As in many places you can or are required to a choose a carrier when purchasing the iPhone. It does not mean the phone is fake. It just means it was intended for a different region.
It's entirely possible the phone you bought is a gray market phone intended for the sale in the Philippines and use with the TNT carrier there. As such its also entirely possible its locked to said carrier.
The only thing you can do is to use your sim card with it and see if it works and is unlocked. If its locked and your sim card does not work with it, immediately return it to where you bought it and demand a refund.
Question: Dear all, I’ve just bought my new iphone 8 plus in Kyiv, Ukraine at local reseller. It was packed and registered at https://checkcoverage.apple.com/ph/en/ But, when I opened it at home, I saw inside the iphone sim-card of TNT. What does it mean?