When migrating your DNS records from a DNS provider to another DNS provider, make sure to follow the following:
- Lower the TTL for your DNS records to the lowest possible value provided by your DNS provider
- Create a copy of the DNS records at the new DNS provider.
- Do NOT delete the DNS records at your old DNS provider.
- Update the name servers at your domain registrar.
It takes about 48 hours for the NS record to be updated as the TLD (Top Level Domains) have a default TTL of 48 hours. For the duration of 48 hours, both your old and new DNS provider will be queried for DNS record information, depending on the cached DNS records information at the Local DNS servers. After you can verify from different locations in the world that the NS record has changed, I would recommend waiting for another 2 days before deleting the old NS records.