In a telephonic meeting, can I ask "Who is this?"

English as a Second Language English Vocabulary, Grammar and Idioms
1

In our tele conference, with our Manager, we sometimes get confused who is on the other side. In such a scenario, can I ask “Who is this?”.
Please observe that we are communicating with our Manager and some Clients (who are very import).
Thanks,
Suresh

2

Hi,

It would perhaps be more polite to ask: Who is this speaking, please?

Alan

By the way the clients are important.