Wrong Domain darn

I have never ran across this until today.

I am moving a client over from one domain to another. I know how to change nameservers. Here is the problem. I created a WP at (lets say) ABC.org.
The client has her old site at ABC.COM. Prior to changing the nameservers from .ORG to .COM I change the WP info to .com.

apparently the nameserver info was given to be incorrectly. I restored her nameservers on the .com site. Now I can not access the .ORG dashboard. I can through FTP access the data on the .org site. I need to edit either one of the wp files or in the database. My question is which one!

Confused and bewildered.

John

Today the client approved the design