i am not sure whether this correct words to describe the problem, but i try my best to explain.
Suppose i deployed a cloud service with A Name. now client ask me give me something good domain name rather than A.cloudapp.net, so according to need i given him fancy domain name A.myapp.com.
After some time they thinks A is not a good name , give me B. so i change the deployment to B.cloudapp.net and then configured custom Domain Name as B.myapp.com.
Client again comes as says my customer is still using A.myapp.com. Can you do something to redirect them to B.myapp.com. with message that it moved to another address.
As i know i used only CNAME and ARecord on domain registrar . how can show a message over there. That this page is moved to other domain.
If A.myapp.com is no longer in the DNS records then the only way that it's still working is that the DNS propagation hasn't taken full effect yet. That can take even up to a few days. Once that happens then A.myapp.com should no longer resolve. This might also be working if you have a wildcard record for @.myapp.com pointing to the same A.cloudapp.net site.
You can create the A.myapp.com DNS record (if it's not still there) and point it to the same cloudapp.net app again, but then in your cloud app look at the hostname as it comes it to the request. If it is A.myapp.com show them a specific page that reminds them this is now B.myapp.com and then redirect them.