sip.ivatel.com.br has no CNAME records.
Question and response
Question
dig sip.ivatel.com.br. NS
Answer
The response has no answer records.
Authority
ivatel.com.br. 10572 SOA ns1.ivatel.com.br. suporte.ivatel.com.br. 1476721570 10800 3600 604800 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0