In this week's Parsha - Shemot Chapter 8 (וָאֵרָא), Pharaoh stands by as Moshe and Aaron perform all of the rites and 'signs' to Pharaoh. After each miracle, the Torah speaks of how Pharaoh's magicians replicated them, at least superficially. After the first two replications, Pharaoh dismisses Moshe's and Aaron's act (the transforming staff and Nile in blood) as just magic. But then after (frogs) Pharaoh demands from Moshe to stop the plague, instead of his magicians? Why not consult the magicians first? I mean if his magicians are replicating all of these 'signs', why not ask them first? What reason was there for Pharaoh to believe that Moshe's acts were different from those of his necromancers?