Putting someone on hold

Just a moment, please.
Could you hold the line, please?
Hold the line, please.

Problems

I'm sorry, I don't understand. Could you repeat that, please?
I'm sorry, I can't hear you very well. Could you speak up a little, please?
I'm afraid you've got the wrong number.
I've tried to get through several times but it's always engaged.
Could you spell that, please?

Putting someone through

One moment, please. I'll see if Mr Jones is available.
I'll put you through.
I'll connect you.
I'm connecting you now. Taking a message

Can I take a message?
Would you like to leave a message?
Can I give him/her a message?
I'll tell Mr Jones that you called
I'll ask him/her to call