Telephony/CPaaS expert needed to design a multi-client answering service (advice + proof of concept)

We are looking for a telephony / contact-center expert to consult us about a centralized answering service. The model: the receptionists will answer inbound calls on behalf of multiple independent client organizations (up to 10 to start, more later) from one shared team. Before we commit to a platform, we want your guidance on the right approach, plus a small proof of concept. The core challenge is keeping each client's world separate. Calls for all clients come into one queue, but every call must be identified by the number dialed, handled with that client's own greeting/script, and, the hard part, fed into reporting where each client's representative can log in and see only their own data and call recordings, nothing from the other clients. Most mainstream phone systems (CloudTalk, Aircall, RingCentral) don't do this multi-tenant isolation natively, so we're looking for someone who can tell us whether to use a purpose-built answering-service platform, build on a CPaaS (e.g., amtelco.com, evs7.com, or other), or take another route. What we're looking for: - Your recommendation on the best platform/approach for this model, and why - A proof of concept showing: a couple of test numbers routing into one queue, per-client identification (whisper/screen prompt), call recording + transcription delivered out by email/API, and two separate client logins each seeing only their own data - Support for 24/7 operation, recording with an announced notice, and voicemail on overflow In your proposal, please include: - Relevant experience with multi-tenant telephony, answering services, or contact-center builds (examples welcome) - Your recommended approach and rough reasoning - Estimated timeline and cost for the proof of concept Please refer to the attached PDF for more info.