Here are some phrases YOU may want use when you are telephoning.
“I’ll pop you through to Mike, then.”
“Can I just run the account no. by you again?”
“You don’t happen to have his mobile number, do you?”
“Bear with me a sec, I’ll just fetch her.”
“Can you just jot down this ref. no, please?”
“Have you got something to write with handy?”
“Do me a favour and double-check the date, would/will you?”
“He’s tied up in a meeting at the mo(ment).”
“I’ve been trying to get hold of him on his landline number all morning.”
“Tell her to give me a call/ring/bell* when she gets back in.” *more colloquial
to pop sb through (verbinden), to run sth by sb (wiederholen), to happen to (do) (zufällig), to bear with sb (geduldig sein), to fetch sb/sth (jdn/etw. holen), to jot sth down (etw kurz notieren), to have sth handy (etw griffbereit haben), to double-check (nochmals prüfen), to be tied up (beschäftigt sein), to get hold of sb (jdn. erreichen), landline (number) (Festnetz)