Apple ID Change / Lost IMessage String

I needed to change my Apple ID and when I updated this on my IPad under General/Settings/Messages I lost my IMessage messages.

Before I do this on my IPhone, is there anyway to prevent this from happening or to restore the lost string? Or even forward the rather lengthy message string?

I did a cloud backup on another device, changed the ID and did a restore, but I didn't have any luck in retrieving the messages.

Thank you for the input!

The messages are tied to your ID if you change it (can't think of a reason for doing so) you won't have access the anything attached to that ID.