Since RoboKiller subscriptions are handled by Apple's App Store, all payments are made from the card linked to your Apple ID. To update your billing method on your iPhone, iPad, or iPod touch:

1. Go to Settings > [your name] > iTunes & App Store.
2. Tap your Apple ID, then tap View Apple ID. You might be asked to sign in.
3. Tap Payment Information, then change or remove your information. To remove the payment method, select None. 
   
4. Make sure that your name and billing address exactly match the information on file with your financial institution, then tap Done.