How would you handle?

[rngrck]

U2 calls illegal pitch by signaling delayed dead ball. B1 hits pitch for a single, runner goes from1st to third. I, Partner says nothing and I as U1 incorrectly interpret the rule and disallow B1's hit and award a ball and put runner at 2nd. Coach argues I don't change my call. I go to my partner after inning, he tells me He didn't want to say anything since I already made my call. I say, if you knew I was wrong, why didn't you get with me and make the call correct. He says, " A good umpire would never rule against his partner". I eventually apologized to the coach and everything was cool.