Does anyone know why Jesus uses two different verbs here?
Here a few things that came up when looking at connections to the word that was used when he says I have called.
◄ 2046. ereó ►
Strong's Exhaustive Concordance
call, say, speak of, tell.
Probably a fuller form of rheo; an alternate for epo in certain tenses; to utter, i.e. Speak or say -- call, say, speak (of), tell.
see GREEK rheo
see GREEK ep
Following the trail to the different word meanings here are some interesting things that came up.
5346 phēmí (from phaō, "shine") – properly, bring to light by asserting one statement (point of view) over another; to speak comparatively, i.e. making effective contrasts which illuminate (literally, "produce an epiphany").
Definition of epiphany;
an appearance or manifestation, especially of a deity.
a sudden, intuitive perception of or insight into the reality or essential meaning of something, usually initiated by some simple, homely, or commonplace occurrence or experience.
φημί; imperfect ἔφην; (from φάω, to bring forth into the light (cf. Curtius, § 407)); hence (from Homer down) properly, to make known one's thoughts, to declare; to say:
So back to your question why two different verbs from calling them servants to calling them friends.
He is telling them a big change has occurred in how he now sees and relates to the people he's talking to. Going from a servant to a friend is a huge change. He's now sharing his thoughts that he's received from God the Father and bringing them into his heart. So he's essentially bringing God down to them as well to let them know God is their friend.