How do I change my iMessage Apple ID?

So, I've had my Apple ID account for quite a few years now when I purchased my first iPhone. My Apple ID (which needs to be a valid email address) was my work email. I am no longer with that company so I'm no longer using that email address and needed to change my Apple ID to a new email address that I just made. I went to appleid.apple.com, clicked manage Apple ID, and changed my Apple ID and primary email address to the new email address I just made. It all went through just fine. I updated my iCloud sign in and I have that all taken care of. But now, whenever I do anything on my phone that requires the pop-up of the Apple ID and then you enter your password, it has my old email address/Apple ID still displayed and I can't figure out how to change it. Also, I went in to Settings>Messages>Send & Receive (which only has my phone number listed) and clicked "Use your Apple ID for iMessage" and that little pop-up saying "Sign in to iMessage" - "Enter the Apple ID password for *****" and lists my old email address/Apple ID. I can not figure out how to change it!!! Please help! I've been at this for hours!!!