IPhone 5 New iCloud address, but still have iMessage from previous iCloud

There are two different ways around this problem.

The first to self help. If you haven't verify the email address that you probably can go back in and change it. Unless you just created this Apple ID hours ago and can walk away from it and just create a second one that is correct, Apple asks for many other pieces of information such as birthday security questions to factor in front Acacian that would allow you to change the one piece of information that's wrong.

The second is to engage Apple customer support. The Apple support webpage will channel you to iCloud account support staff and it will typically be a web form where you can place your correct contact information and explained the mistake you made. They might be able to assist you with things that you can't do for yourself. Additionally, they speak many languages and can often educate you about your options better than a catchall procedure on the Internet can.

My experience is you cannot actually delete an iMessage once and have it delete elsewhere.

You can only delete the local cached copy of a message to suppress it being showed/stored on that one device. If you turn off iMessage and turn it back on, you will see the messages from iCloud come back whether you deleted a message or not.