Change your payment method iPhone or iPad
If you purchased your subscription in your iPhone or iPad, the payment is processed through Apple App Store. The payment method used is the one you have associated to your Apple ID.
To edit your payment information:
Go to your iPhone or iPad Settings
Tap your name.
Tap Payment & Shipping. You might be asked to sign in with your Apple ID.
From here, you will be able to: add a new payment method, change your payment method information or delete a payment method.
Here is a link from Apple support that explains how to manage your Apple ID payment information in the Settings of your iPhone or iPad:
You can also check here what payment methods you can use with your Apple ID to buy your Mojo Subscriptions in the App Store.