A phone that is NOT in a call group rings when a call comes in, how do I stop it?

I am the front line of the phones, and we have a setup where it rings on my mobile first (RingCentral App), then my physical phone in the office, then it rolls over to a group. However, every time a call comes in, one of the phones at the office will always ring 4 times before it goes to the front desk. The phone it is ringing on is not listed at all in my call group. My settings are all correct, we cannot figure out why this phone is ringing.