How to display the name "BESTSELLER" at the product, like "NEW" PS 1.6

[Prestaraf]

I try something like this but not work 

{if isset($best_sellers) }
  <a class="best-box" href="{$product.link|escape:'html':'UTF-8'}">
      <span class="new-label">BESTSELLER</span>
  </a>
{/if}

some idea?

[Rhobur]

Alternatively, you could go to Localization->Translations->Modules Translations search for the bestsellers module and do your change there.