The file you changed in cart/includes/languages/english/custom/ was for the 'custom' template, where 'custom' is intended to be a place-holder for your current template's name.
Try moving the changes you made into cart/includes/languages/english/responsive_classic directory, since responsive_classic is the template you are currently using.
Note, too, that you should "clone" that built-in template before going too far with your editing. Here's a link to the Clone a Template plugin: https://www.zen-cart.com/downloads.php?do=file&id=2087
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