Multi-Tenant Hosted PBX Platform Development

Hi,
I'm looking for an experienced VoIP developer to build a complete multi-tenant hosted PBX / UCaaS platform with real-time billing and a modern client portal. The system should be scalable, secure, and production-ready for a hosted PBX reseller business.
Tech Stack & Requirements:

Core PBX:
FreeSWITCH + FusionPBX (latest version)
True multi-tenant setup with domain isolation
Superadmin + tenant admin access levels
Enterprise features configured:
ACD/Call Queues (strategies, agent states, callbacks, wallboards)
IVR, Ring Groups, Time Conditions, Call forwarding with CC/CAP
Call Recording, Conferencing, Voicemail-to-email
Secure WebRTC (wss) for browser-based calling
Call Center modules and reporting
High availability & security (Fail2Ban, iptables, SSL)


Real-Time Billing:
Integration with CGRateS for live charging (prepaid/postpaid)
Balance enforcement during calls, concurrent call limits, fraud protection
Rate tables, destination-based pricing, CDR flow to portal
Modular setup (LCR optional)

Client Portal:
Modern frontend in React (clean, responsive dashboard)
Backend in Python (Django/Flask preferred for APIs, logic, webhooks)
Features:
Public landing page with services/pricing
Secure signup/login
Client dashboard: Balance view & refill, CDRs/call history, SIP credentials, active services
Payment gateway integration (modular code supporting multiple providers via webhooks for automatic balance top-up)

Deliverables & Ownership:
Full source code (PBX configs, Python backend, React frontend, scripts) (I will be owner)
Clean, commented, modular codebase
Complete documentation: Installation guide, architecture overview, how to add tenants/rates/providers, backup/update process
100% IP rights transfer to me
30 days post-delivery support for bug fixes

Preferred Experience:
Proven projects with FreeSWITCH + FusionPBX multi-tenant setups
Strong React frontend + Python backend development
VoIP billing (CGRateS)
Payment gateway integrations (webhooks)
Portfolio or links to similar hosted PBX/UCaaS platforms

Please share:

Relevant past projects (screenshots/links)
Fixed-price quote
Estimated timeline