@Dani_Solis Where are you adding this formula? You cannot refer another column in default value formula for any column.
Do you want this choice column to be editable by users from list forms? If yes, you may need to use Power automate flow or Power apps customized list form to automatically update choice column value based on another column.
If you don't want choice column to be editable by user, you can use calculated column instead of choice column as suggested by @RobElliott
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