New Zoom IP Phone Causing Disconnect

Hey there community,

The way I have the system configured is through 1 x phone number, with 3 x extensions (Reception, Clinician, and Support: 2 of which have calling packages) and the Yealink IP Phone is assigned to Reception. When Reception is on a call and the Clinician starts a call, it disconnects the Receptionist. Vice versa is also occuring.

Any help is appeciated.

TIA.