Yes, we do have a Multi-Tenant module you can install on VitalPBX. This will allow you to have multiple clients using a single instance.
The tenant will feel as if they where individual PBX systems, even though they belong to a single installation.
https://vitalpbx.com/multi-tenant-pbx/
Tenants can even have the same Numbering Plan! Meaning that Tenant A can have extension 1000, and Tenant B can have extension 1000. You can even set it up so extension 1000 of Tenant A can call extension 1000 from Tenant B.
You can get an in-depth look into this module on this video we made about it.