Here is how you can rewrite pages that are inside a folder. It also works in wordpress.
RewriteRule ^phones/phone-page-(.*).html /phones/index.php?page=$1 [L]
In the example, “phones” is the folder. http://incvice.com/phones and /phones/index.php is the actual page (located in the /phones/ subfolder).
This will work, just add the code inside your .htaccess file.