> Twilio will get in trouble with Visa/Mastercard if customers say Twilio is dropping them for disputes the card provider finds in the customers' favor.

This isn't true. Visa/Mastercard care about your chargeback rate. You can block a customer who's done a chargeback. I'm sure the card networks have rules around what you cannot do as a result of a chargeback but you can stop providing services to a customer who has done a chargeback.