There are two types of name servers that make up DNS: authoritative and recursive name servers. To use Cloudflare you need to change your domain's authoritative DNS servers. OpenDNS, Google DNS and ISPs relate to recursive DNS. So, you can continue to use whatever recursive DNS server you want.
Still not finding what you need?
The CloudFlare team is here to help. 95% of questions can be answered using the search tool, but if you can’t find what you need, submit a support request.