3CX is an open-standards IP PBX which can be deployed on Windows, Linux or in the cloud (Google, Amazon, Azure). It offers a complete suite of Unified Communications features such as chat, web conferencing, smartphone apps for iOS and Android and more. 3CX will not only cut your telco costs by up to 80%, it's also easy to manage, maintain and use for both the admin and user. Try it for free here.
Quick start guide how to use a DECT handset behind 3CX
Quick start guide how to use a Maxwell behind 3CX