Assuming you had sufficient funds in your PayPal account balance, your PayPal account should have been used. Below is how the process is supposed to work. As this is a peer to peer community, we don't know why your other funding source was selected - you may want to contact customer support with your concerns.
PayPal will first check your PayPal balance to see if there is enough money to cover the payment.
If you have enough money in your balance, PayPal will use it to make the payment.
If you have some money in your PayPal balance but not enough, PayPal will use that balance plus another payment method linked to your account.
If you don’t have any money in your PayPal balance, PayPal use another payment method linked to your account.
When you don’t have a PayPal balance or don’t have enough in your PayPal balance, PayPal will use your bank account as the default payment method unless you select a different way to pay.
To make sure you’re using the payment method you want, check the Review Your Payment page.
Additional Notes:
You will be able to select a preferred funding method for payments made through the regular checkout process as well as Goods and Services via Send Money. You will also have the option to select a different preferred method for online purchases vs. in-store purchases.
If you have PayPal Smart Connect, PayPal Plus MasterCard, PayPal Extras MasterCard, PayPal Debit MasterCard, or eBay MasterCard, you can make that your default payment method. Once a payment has been sent to another PayPal account, the funding source cannot be changed.
