Apex domains cannot have CNAME records.
Question and response
Question
dig intdev.exetel.com.au. NS
Answer
intdev.exetel.com.au. 5 NS ns-1140.awsdns-14.org.
intdev.exetel.com.au. 5 NS ns-1785.awsdns-31.co.uk.
intdev.exetel.com.au. 5 NS ns-455.awsdns-56.com.
intdev.exetel.com.au. 5 NS ns-777.awsdns-33.net.
Authority
The response has no authority records.
Additional
ns-455.awsdns-56.com. 1 A 205.251.193.199
ns-777.awsdns-33.net. 1 A 205.251.195.9
ns-1140.awsdns-14.org. 1 A 205.251.196.116
ns-1785.awsdns-31.co.uk. 1 A 205.251.198.249
ns-455.awsdns-56.com. 1 AAAA 2600:9000:5301:c700:0:0:0:1
ns-777.awsdns-33.net. 1 AAAA 2600:9000:5303:900:0:0:0:1
ns-1140.awsdns-14.org. 1 AAAA 2600:9000:5304:7400:0:0:0:1
ns-1785.awsdns-31.co.uk. 1 AAAA 2600:9000:5306:f900:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0