An easy this week...
“I don’t know”
Why? Clients don’t care what you don’t know; they care about how you will help.
“Let me look into that. It will take about 5 minutes, would you like to hold or should I call you back?
“Let me put your through to Siri, she takes care of that”
BTW: If you've got an expression that you dislike hearing during a customer service interaction - email it to me and I'll post the re-write.