You do this by changing a term to the url in the address bar. If you want to change it to English, for example, do the following:
?lang=en
Which would look like this in the address bar: https://admin.taxicaller.net/admin/users.php?lang=en
You can do the same to change to the following languages:
Swedish: https://admin.taxicaller.net/admin/users.php?lang=sv
Spanish: https://admin.taxicaller.net/admin/users.php?lang=es