A lost phone should be treated like a lost card. You should inform your Account Holder to cancel your card or if you are the Account Holder you can by logging into your Online Service Centre account and navigating to Cards → [Select card] → Settings → Report Card Lost , Stolen or Damaged. You can also order a replacement card in the process.
Note that If you report your card lost or stolen, your card will be cancelled straight away. If you report it damaged, your card will still be active for 10 days until your new card arrives.