Apex domains cannot have CNAME records.
Question and response
Question
dig wisperisp.com. NS
Answer
wisperisp.com. 5 NS dns1.wisperisp.com.
wisperisp.com. 5 NS dns2.wisperisp.com.
wisperisp.com. 5 NS dns3.wisperisp.com.
Authority
The response has no authority records.
Additional
dns1.wisperisp.com. 5 A 192.68.255.156
dns2.wisperisp.com. 5 A 192.68.255.158
dns3.wisperisp.com. 5 A 45.63.67.224
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0