I have been having some issues with a certain network supplier over unchanged nameservers making my site invisible to their customers. I wouldnt be bothered except that they are one of the largest ISP's in Ireland.
They claim that the records are still active on the old nameservers for my site so therefore they shouldn't change until they get a response telling them there are no dns records for the site.
My question is, what is the correct behaviour? Every other network provider, isp, dns server on the web has updated to my new nameservers.
Are they following some technically correct but ignored RFC that says they don't need to check new nameservers until the old ones return an error?
Vodafone eventually contacted me and have said they have resolved the issue, and more importantly are now escalating it to their correct technical staff so this issue shouldn't affect anyone else. Hope this solves the issue.