When using PayPal as the payment method to fund your Twilio account Twilio will use the default PayPal payment methods defined in your PayPal accounts preferred payment hierarchy. This is explained here in PayPal's About Payment Methods page.
Twilio does not support the ability to select the payment method charged within your PayPal account.
- To change your PayPal payment method, please see PayPal's guide What payment methods can I use with PayPal? (PayPal.com)