Welcome to Android Central! In Settings>About Phone, what's the exact model number listed? Does the phone also have a sticker on the back, or do you have the original box? If so, what model does it specify there?
It's not that uncommon for a seller to flash a different region's firmware to a phone in order to make it more compatible. Unfortunately, this can sometimes also cause glitches, since the a given phone doesn't always work well with other firmware.