When I ask my friend for directions to his residence over the phone, which of the following instruments of knowledge, as per the classical Indian school of logic (Nyaya), is used by me to hear what my friend says?

Hearing the friend's words is an act of perception (Pratyaksa).

The ear making direct contact with sound is auditory perception.

Pratyaksa is knowledge from sense-organ contact with an object.

Though the message is verbal, grasping the sound itself is sensory.

So the instrument used simply to hear is perception, not testimony.