Werewolves do not exist.
The idea of the werewolf comes from a medieval misunderstanding of two diseases, hirsutism and rabies. The popularity of werewolf stories really began in the 1990's in fantasy novels and in films like "Twilight". But actual werewolves do not exist.
Furthermore, no magic or spells will turn you into anything other than the person you are. You cannot become a werewolf, a vampire, a mermaid, an angel, a fairy or anything of the like. You cannot grow wings or change the shape of your body.
Real magic does exist, but it is not like it is in fantasy novels and Hollywood films.