"You are speaking on the telephone."

Translation: Telefonálsz.

[deactivated user]

"A telefonon beszélsz" is a more literal translation. The one offered (telefonálsz) would be "you are calling" in English. This should be clarified or changed.

[hatcher]

"you are calling" is "hívsz". "telefonálsz" would be "you are phoning"

[Djenthallman]

Why is Telefonál not accepted? It could be formal singular 2nd person. Reported.

[Kingstanding]

You're phoning.