I would like to convert my current prefix value to another prefix value, basically text rename. For eg abc.domainname.com to xyz.domainname.com

Below is what I have tried so far.

RewriteCond %{HTTP_HOST} !^abc\.
RewriteCond %{HTTP_HOST} ^([^\.]+)\.domainname\.com$ [NC]
RewriteRule ^(.*)$ https://xyz.domainname\.com/%1

Can somebody tell me what I am doing wrong? Thanks