Possibly. Although this would mark a clear demarcation line between these services that offer a genuine trial period and those who just count on your forgetting to cancel or deliberately try to make cancelling difficult or time-consuming.
Or $1 trials when it's a MasterCard CC, then no need for a text/email.
That sounds like it would be against the merchant agreement. Plus, unless you are your own payment processor, how would you know the card type?
All Visas start with 4 and MC start with 5. I think you're right though, I doubt they allow price changes based on card type.
How would you see the credit card number at all unless you are the payment processor? Payment processors show the interface into which the credit card number is entered.