Apex domains cannot have CNAME records.
Question and response
Question
dig convergys.com. NS
Answer
convergys.com. 2 NS ams-ns.cvgs.net.
convergys.com. 2 NS odc-ns.cvgs.net.
convergys.com. 2 NS cdc-ns.cvgs.net.
Authority
The response has no authority records.
Additional
ams-ns.cvgs.net. 2 A 193.104.192.200
cdc-ns.cvgs.net. 2 A 206.126.168.200
odc-ns.cvgs.net. 2 A 206.126.185.200
cdc-ns.cvgs.net. 2 AAAA 2620:103:90d2:3003:250:56ff:febb:60
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0