It is perfectly fine for a smartphone brand to exist in just one country—and for no such companies to exist elsewhere—especially since smartphones are generic devices meant simply for use; while their designs may constantly change, their core purpose remains the same. So, it is acceptable for a brand to be limited to a single country; even if the smartphone is expensive, one can save up to buy it, provided it is within reach.
If someone says they are a huge fan of a brand, just say "fine, just" that you agree with what they're saying, and that it's okay for there to be only one brand in the world in a single country.