The name of the Seur carrier is used in these four shipping modules:

\includes\languages\spanish\modules\shipping\table.php
\includes\languages\spanish\modules\shipping\perweightunit.php
\includes\languages\spanish\modules\shipping\item.php
\includes\languages\spanish\modules\shipping\flat.php

So you have to edit the one you are using.
If you are using Windows I recommend you try Windows GREP, you would have found these references very easily.