As I understand it, the three witches do not have any control over Macbeth's fate. What they can do is predict the future--and the future is unchangeable. As far as Macbeth controlling his own fate, that is impossible, although that is exactly what he tries to do. It was inevitable that he would murder Duncan. Shakespeare's message in this play is fatalistic. Whatever is going to happen to Macbeth--or to us--is already predetermined. There are some scientists and philosophers and others who believe that everything that happened and will ever happen after the Big Bang was predetermined because every effect has to have a preceding cause, and there is an unbreakable chain of cause and effect leading from the Big Bang throughout eternity. Whether or not this is true, it is implicit in Shakespeare'sMacbeth. Macbeth tries to prevent Banquo's heirs from becoming kings instead of his own children and their heirs. It cannot be done. Fleance escapes. There is a significant passage in Act 4 when Macbeth is consulting the three witches and is warned against Macduff but assured that "none of woman born / Shall harm Macbeth." He says:
Then live, Macduff; what need I fear of thee?
But yet I'll make assurance double sure
And take a bond of fate.
Here we see Macbeth at his most ambitious, arrogant, headstrong, belligerent, and unreasonable. Imagine demanding a bond from Fate itself. None of us can even be sure of what is going to happen to us tomorrow. But according to the philosophy implicit in Shakespeare's play, whatever happens is already predetermined and inevitable.