How could I say "who is this"? especially whilst on the phone could it be "bu kim"?

Thank you

I think they say sometimes: " o kimmiş ?"

You mean: "Who am I speaking to?"

My try:

Kiminle görüşüyorum?

Wouldn´t it normally be ´konuşuyorum´   ?

 Turks use to say "görüşmek" when they ask at phone " can i speak with.."

Interesting. Thanks.