That <br /> is added to both the image and the text in the functions file:
/includes/functions/functions_prices.php

Code:
    // If Call for Price, Show it
    if ($product_check->fields['product_is_call']) {
      if (PRODUCTS_PRICE_IS_CALL_IMAGE_ON=='0') {
        $call_tag = '<br />' . PRODUCTS_PRICE_IS_CALL_FOR_PRICE_TEXT;
      } else {
        $call_tag = '<br />' . zen_image(DIR_WS_TEMPLATE_IMAGES . OTHER_IMAGE_CALL_FOR_PRICE, PRODUCTS_PRICE_IS_CALL_FOR_PRICE_TEXT);
      }
    }
You would need to alter the code to change that ...

NOTE: function files do NOT use override files ...