It is really sad to know that so many educated people believe in pirs, magic etc.
The 'Auliya Karam' were the people who were very pious and close to Allah and all what they did was to preach Islam and make the people understand it better and set example before them in their person. They shouldn't equated with pirs.
Moreover, the holy prophet (pbuh) was never under any spell at all. The last two surrahs don't reveal any such info to us. These surrahs are prayers to seek Allah's protection from many ills, ill effects of the things He created etc.