It's super simple to update your billing details for your subscription payments and SMS recharges. To update your billing details simply follow these steps:
Navigate to Settings > Locations
Select the location you wish to update the details for
Scroll down until you reach the billing section
Click the update payment method button (make sure you do this for both Subscription Fees & SMS recharges if you need to).
6. Add your new card details you wish to use & press Add.