1. AT&T Inc.
2. Avaya Holdings Corp.
3. Cafex Communications Inc.
4. Cisco Systems Inc.
5. Google LLC
6. International Business Machines Corp.
7. Microsoft Corp.
8. Oracle Corporation
9. Plantronics Inc.
10. Plivo Inc.
11. Polycom Inc.
12. Ribbon Communications Inc.
13. TWILIO Inc.