The received/transmitted audio may be low because the headset cable is connected to the wrong port on the phone. Connection to the wrong port may cause low audio or even permanent damage to the headset. Make sure the Jabra flat cord with modular connector is inserted into the headset port on the desk phone. The headset port is typically marked with a headset icon.
The following pictures of the desk phone show the location of the correct headset port, which shows a headset icon, and the incorrect AUX port.
