[SOLVED] How make sound volume of door telephone

[firejim]

I was trying to make sound volume for the door telephone but what I made is turn of and open volume only. I would like to have increase or decrease the volume. i will upload the circuit

 

[firejim]

Sorry for late here is the pcb, I would like to avoid a switch on/off and recommend something like volume capacitor

 

[firejim]

at last I succeeded to put potentiometer in the phone