Hi Leandro,
I have tested this locally, using pt_BR as my default installation culture. Unfortunately I was unable to reproduce the issue. I was successful in setting different URLs in the Admin > Settings > Site information > Base URL for different cultures, and AtoM always served up the link based on what I had entered in the field, depending on the language I was browsing in. For example, I managed to set the English UI to
10.10.10.10/atom and the Brazilian Portuguese UI to use 10.10.10/atom2, and each time, the reports directed me to the expected link.
It's possible that this is a caching issue - have you tried restarting services and clearing the application cache again since you changed the Base URL settings? If not, I suggest trying it again now.
Note, I would also strongly recommend you test in a new Incognito browser window - it's possible that your browser cache is serving you the old, cached page! When you use an Incognito or Private window, usually browser caching is disabled by default.
If none of this works, then you might want to review your webserver settings, and make sure there are no redirects or other factors that might be affecting this?
Let us know how it goes.