With Vorco Calling for Teams there are several components that make up the entire service.
This comprises the Office 365 cloud environment that provides the Teams service as well as all the other associated services like Exchange Online, SharePoint Online etc. Any issues with the Teams client (desktop/mobile app, Teams desk phones) are between the customer and Microsoft.
This is the service that provides inbound and outbound call termination between Microsoft Teams and the Public Telephone Switched Network (PSTN). You use this when you dial phone numbers from Microsoft Teams, and when inbound phone calls come into Microsoft Teams. Any issues with being able to make and receive calls (e.g. can't ring a certain number, or a certain number cannot ring you) are between the customer and Vorco.
We've added an asterisk to this one because sometimes Vorco is responsible for the network.
The customer is responsible for their internal network like switches, wireless access points, routers (unless it's a Vorco managed router) and buying adequate connectivity to meet your needs (Vorco can scope and supply suitable connectivity).
Vorco is responsible for having adequate connectivity between our Session Border Controllers and Office 365.
Because Teams is very mobile, users can make calls anywhere they are including on home Wi-Fi, mobile 3G/4G data, international roaming data, hotel Wi-Fi etc. This is the customer's responsibility to ensure adequate connectivity back to Vorco's network. It's not realistic to control all these situations, so customers should set expectations with staff that call quality/delay may vary when away from the office and that Vorco won't invest large amounts of time into any issues reported in these situations.
Vorco operates Quality of Service within our own network and will ensure any media (audio/video) flowing between our Session Border Controllers and customers connected with Vorco Internet has priority. However there are cases where Microsoft handle media across the Internet (meetings and auto attendant functions). Where media leaves Vorco's network, it also leaves Vorco's responsibility.
The customer (or the customer's IT provider) is responsible for appropriate configuration of Microsoft Teams features like where to route inbound calls. The customer is also responsible for suitable Microsoft Teams client selection and setup such as desktop application, iOS/Android applications, physical desk phones, meeting room equipment.