電話対応 Answering the phone

so when the 内線 rings, I can't ever catch the 課 or whatever that's calling, but I might be able to catch the name.
How can I ask them to repeat their 課 before transfering the call to my coworker?

Am I just overthinking it? I get nervous and default to telling my coworker 「どこかのOOさんからのお電話です」and then my coworkers will either chuckle or look annoyed that I didn't confirm which department the call is from ;-;