See here for the end of support announcement for Hybrid Call Service.
After the above deadline, new customer organizations that are created in Control Hub can no longer set up Hybrid Call Service for enterprise calling integration with the Webex Teams app. Existing customers already using Hybrid Call Service are not impacted. Cisco Webex Devices in shared mode will continue to support Hybrid Call Service through the Webex Device Connector with no impact in functionality. New devices in personal mode won’t have access to hybrid calling until further notice.
Whether new customers or existing customers, Calling in Webex Teams (Unified CM) is the recommended option for continued support. This solution provides softphone capability to Webex Teams users and is continuously updated with new features and functionality. In this architecture, the Webex Teams app registers directly to Unified CM for enterprise calling capabilities.
When Webex Teams is registered with Unified CM, the solution provides enterprise calling capabilities—audio/video calls and mid-call features such as mute, consultative transfer, merge/conference, sharing, and so on. Direct access to call settings such as call forwarding (CFA), single number reach (SNR) and visual voicemail is also supported. Webex Teams app also interfaces with Unified CM-registered desk phones to provide remote call control capabilities in Deskphone Control (DPC) mode.
Additionally, direct registration to Unified CM provides these benefits:
Direct connection to Unified CM leading to a faster connect time than Hybrid Call Service
Direct media when Webex Teams apps are local within enterprise network
Additional calling capabilities with a roadmap towards Jabber calling feature parity
Reuse of existing MRA and Jabber CSF configuration for client-side integration (unlike Hybrid Call Service’s server-side integration)
Deployment Guide for Calling in Webex Teams (Unified CM)
Deployment Guide for Hybrid Calling for Cisco Webex Devices