Pbx for local user that can connect to 2 different node at the demand

A club I help with to maintaining 2 repeater’s want to have secured PBX to give their older user that live in retirement home the capacity to connect to either of the repeater on demand by calling an extension.

I know I could make a sip user for each member and enable chan_sip but that would mean 2 different sip account to enable at each user.

Anyone can help me set a secured pbx that would connect to the IAX trunk of both repeaters And the user would only need to dial the node number to be able to use their phone. Don’t want to put the sip port available for security reason especially on the raspberry pi’s

Pierre
VE2PF

By “older user” am I correct in assuming licensed hams? If so, is there a radon EchoLink will not be useful?

Thanks,
Bob
K6ECM