Change your billing info on the Play Store

To change the billing info associated with your MobiSystems subscription made through the Play Store do the following:

1. Sign in to your Google account and go to Subscriptions.
2. Find the MobiSystems subscription you want to edit and click Manage.
3. Under the card you’re currently using to pay, click Change payment method. If you don’t see this option, click Manage payment methods.
4. Choose a new payment method.
5. Choose Submit.

On Google Play Store you can set a back up payment method:

1. Sign in to Subscriptions.
2. Find the MobiSystems subscription you want to edit and click Manage.
3. Under the card you’re currently using to pay, click Change payment method. If you don’t see this option, click Manage payment methods.
4. Choose Update backup payment method.
5. Choose a payment method.
6. Choose Submit. 

Have in mind that on Google Play Store some payment methods can't be used for subscriptions. For more info contact Google support.