I have a rotary phone that used to work with our xfinity land line. The phone still rings when we receive a call and I can answer incoming calls. But I'm not able to make outgoing calls. I get a dial tone but can't dial out. From reading other questions on this forum, it appears that, depending on the modem I have, it may be possible to have rotary dialing turned on. How do I find out if this is possible for me?