Using CaptionCall Bluetooth Phone with Phonak Bolero M90

My wife is trying Phonak Bolero M90 aids. We have a landline with a Caption Call & an AT&T Dect 6.0 answer system with 5 handsets. The aids do not have a telecoil, her old Unitron aids did. The AT&T handsets have speaker phone available which helps. To get use of caption call need to use Bluetooth. Problem is if my wife uses a handset instead of Caption Call Bluetooth keeps dinging in the aids. Is there way to mute the Bluetooth signal in the aids? For better speech understanding she needs Caption Call with sound to both aids. The answer may be answer via handset then walk to Caption Call & switch.