Telekom CompanyFlex Cloud PBX 2.0 for Windows

https://geschaeftskunden.telekom.de/business/produkte/internet-festnetz/tarife/companyflex/cloud-pbx

Telekom CompanyFlex Cloud PBX 2.0 is a cloud-based, virtual telephone system from Deutsche Telekom designed to enable flexible, location-independent business communication. It integrates smartphones and desk phones into one system, offering features like virtual conferencing, chat, presence management, and seamless call handover between devices.