You can try a software PBX solution -- I've spun up quite a few 3CX deployments using Twilio as the SIP provider. Then you can call in a number of ways (super configurable routing inbound and outbound). There's a "softphone" mobile app for internet -> sip calling on smart phones. 3CX has pretty reasonable licensing (I think there may still be a free tier) and Twilio is super cheap.