Advice for talking on the phone?

Advice for talking on the phone? Hi everyone, I have an important phone call coming up in 3 hours with someone in upper management in my field of study and I really want to make a good impression and not stutter as much. My stutters worsens when on the phone. What tips or advice should I follow to better my fluency? Any tips or advice are deeply appreciated, thank you! Update: Thanks for the advice everyone! It did not not go unnoticed! Def helped! I stutter severely on the phone but for the call it was just moderate. Was asked to only repeat myself once! Thanks everyone! The guy even said to not hesitate to call him again and he’s willing to help out