CallTower

CallTower occupies a different position from everyone else on this shortlist: rather than selling its own collaboration suite, it makes the platform you already chose work as a real phone system. Its center of gravity is Microsoft Teams voice, native calling delivered through Operator Connect or direct routing, with the carrier relationships, number management, licensing, and support handled as a managed service, and it does the same for Cisco Webex and Zoom Phone. That fills precisely the gap Microsoft leaves: companies get Teams calling without building telecom expertise in house, and multi platform environments, Teams for most of the company and Webex or specialized voice elsewhere, get one partner across all of it. Regulated industries value the compliance options and the accountable support relationship. This is a scoped, managed model with quote based pricing, not a self serve platform with a public price list, and businesses that want a single vendor's native suite end to end are better served above. For the specific and very common problem of making Teams a dependable business phone system, CallTower is what the solution looks like.