If you own a tablet (such as the Apple iPad) and you are able to make a call, the usual process of top-up according to the top-up instructions of your provider applies, as described in the email.

If necessary, it's possible to call using WiFi (with apps such as Skype or Viber), or you could simply place your sim card in a different device.

Should you need help, the customer service of your provider is able to top-up your code manually.