Can I change my payment source in PayPal?

Yes, you can. 
You can change your credit or debit card details in PayPal to make payments to pre-approved billing easy.

Updating your payment method in PayPal (also known as payment source) will ensure orders can be charged and you will be notified when a payment is declined or if you need to update an expired/incorrect credit card.
Alternatively, you can also choose to add money to your PayPal balance. This is the easiest method to cover the cost of the purchase. After making changes, please notify your seller so that the order can be charged.

​Follow these steps to change credit or debit card details:

1. Log in to your PayPal account.
2. Go to Profile. 
3. Click Profile & Settings.
4. Select Selling tools.
5. Select Update under my automatic payments.
6. Click the pre-approved payment plans link.
7. Select the correct Vtiger preapproved payment charge. When the order is placed, buyers will have received a confirmation email from PayPal with the preapproval key.​
8. Click the Change link at the bottom of the screen.
9. Select or add a new payment source.
10. Click Save.

Once you are done changing the card details, notify the seller so that they charge the order.
To know more about PayPal, click here.