Rewriterule Problem (HTACCESS)

Question

I have the following HTACCESS code:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule ^customer/$ index.php [L,NC]
</IfModule>

(I cleaned the rest of the code to simplify.)

In the folder that HTACCESS is in (not at the root), you have a file Customer.php

When I’m going to test, instead of "play" to index php., he "plays" for Customer.php

If I change the code to, for example:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule ^customers/$ index.php [L,NC]
</IfModule>

or

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule ^qqercoisa/$ index.php [L,NC]
</IfModule>

He runs with success.

Could someone help me?