ns1.csgsystems.com has no CNAME records.
Question and response
Question
dig ns1.csgsystems.com. NS
Answer
The response has no answer records.
Authority
csgsystems.com. 557 SOA ns1.csgsystems.com. postmaster.csgsystems.com. 2014021664 900 600 1209600 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0