iTunes:
https://support.apple.com/en-us/HT201266
Google play:
https://support.google.com/googleplay/answer/4646404
Web:
You would be able to change your billing information here: https://cp.bluesnap.com/jsp/account_login.jsp
If you do not have a password you can set one by selecting "forgot password" which would allow you to set one. You would be able to find the "order id" on the invoice in the Magisto "account settings" page.