Franz Recast a Spell when I made a Correction

Franz automatically rolled damage for my Magic Missile spell. When I asked him to allow me to roll damage, he cast the spell again without letting me roll for damage, killed the enemy, and used an additional spell slot. Spells in combat need serious attention. Playing a spellcaster as of right now is extremely frustrating as I have to constantly correct improper modifiers being added and incorrect spell effects. Whenever I make a correction, Franz always recasts the spell and uses an additional spell slot. Only 50% of the time does Franz heed the correction.