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The phone is an analog phone unfortunately. The letter Volvo sent out to customers a couple years ago along with the tech note we received stated that the phone support would be completely gone some time ago. 911 support was supposed to be continued for a while, but I think even that's expired now. There is no way to get a new subscription for the phone.
However, if you call your local Volvo dealer, there was a customer satisfaction update for the installed phones. Volvo paid to have the phone removed, a dash cubby put in the hole for the phone, and a software download to remove the application from the car. The software gets rid of the "On call plus deactivated" message and removes the phone from the car configuration. If you have the corded phone in the armrest, Volvo didn't pay to remove it. You have to get a new center console armrest pad or leave the phone there.
There is a Volvo blue tooth handsfree accessory module available. It allows the use of handsfree bluetooth phones and uses the audio amplifier and front speakers. There is a handsfree mic. that is installed up on the panel next to your sunroof switch. Takes about 1 to 1.5 hours to install.
Hope that helps!