2 different theme shows in url

hey, guys, anyone helps me how to fix my website shows 2 different themes in URL one www and 2nd without www.
here are both URL:

https://www.sastablogger.com/

https://sastablogger.com/

Redirect one url scheme to another.

If you want to keep www version then redirect non www version to www or vice versa.

Wordpress automatically takes care of it. Make sure that site and homepage url is same in setting.

Insert this code in htaccess file

I think his question was more on the lines of how could that happen. The website shows 2 versions, one for the www and one for the non-www version. I have came across this issue when migrating the website on a new server and doing a wrong nameserver change, so the www version was moved, but the non-www wasn't. Try to see why does your website point to two versions at the same time. The easiest fix is to redirect, as people said. But check to see why did it happen in the first place