Zoom Phone Audio

Our community has a couple of elderly members who do not have computers and struggle to connect using the telephone connection method. We added Zoom Phone to our plan hoping that, after we had started our Zoom call with other members of the community, we could simply call our two elderly members. We discovered that when they connected nobody else in the Zoom room could hear them. I tried to understand some of the ways to merge the call, but it seems like it is only if everyone is on the phone. Is there a way to use both Zoom Phone and the Zoom Room at the same time?