Do i know who is speaking? means kya main jaanta hun kaun bol raha hai.
So this isn’t what you meant, right? Therefore, the correct translation is ‘May i know who is speaking? (kya main jaan sakta hun kaun bol raha hai?)
chaurasiya@ when we request something we use- may, could. so you should use “MAY” instead of “DO”. for eg: may i know who is speaking?( kya main jaan sakta hoon kayun bol raha hai)
