Domain Change error

I have a new domain. I am trying to replace my current WordPress custom domain with the new one (GoDaddy). Go Daddy told me to just add replace the old domain name in WP with my new one. I did that. GoDaddy neglected to tell me to have point to my WP Nameserver prior to making this edit. Now, I cannot log into my WP dashboard. What happens is, if I type the old url, it pulls up the site, but when I click login, it redirects the new domain I entered in WP. Because that URL doesn’t actively point to the WP nameserver it errors.

I have read all the documentation and it looks like I need to FTP the edits. We have always made all edits in WP and have never FTPed anything.

Currently I am using a redirect to make my site viewable. I just cannot login to edit it.

Can you please help?! The former URL was ATXjammers.com. The new one is JammersLacrosse.com I think the easy solution is to simply change the URL back to ATXjammers.

BTW, I opened the account I am using here per the Happy Engineers.