provr1.oi.com.br has no NS records.
NS records for this zone are defined at oi.com.br.
NS records for this zone are defined at oi.com.br.
Question and response
Question
dig provr1.oi.com.br. NS
Answer
The response has no answer records.
Authority
oi.com.br. 300 SOA ns01.oi.net.br. hostmaster.oi.com.br. 414275585 600 1800 604800 300
Additional
. 0 OPT ; payload 4000, xrcode 0, version 0, flags 0