Your PHB is correct: Weapon Master does not grant you a fighting style
The Weapon Master feat (PHB, p. 170) grants you:
- +1 to your Strength or Dex, to a max of 20.
- proficiency with four simple or martial weapons of your choice.
There's no mention of acquiring a fighting style. Modifying the feat to include one would be introducing homebrew to your game.
No other official feats currently allow a PC to learn a fighting style, either.
Note: One possible source of your confusion (suggested by linksassin in the comments) could be the similarly named Great Weapon Master feat (PHB, p. 167) - which is different from the Weapon Master feat, but also doesn't grant a fighting style - and the name of the Great Weapon Fighting fighting style.
The Great Weapon Master feat and the Great Weapon Fighting fighting style work well together for obvious reasons. There is no overlap in the benefits they provide.