Yes, we stopped accepting new Amex cards some time ago. But for members who had cards on file, we have continued to process payments, until that card stops working for any reason. So maybe a transient decline or other issue caused is to be removed from the account. That said, I believe the entire relationship with Amex is winding down soon.
Today we accept Visa/Mastercard or ACH (bank account draft) for payment for Sonic services. You can make adjustments to your payment method at: https://members.sonic.net/account/billing/options/
BTW, the why behind all of this: Amex charges larger fees. Those fees are passed on to all of our members in their subscription costs, so in order to save everyone those costs, we seek the most efficient bank clearing method. ACH is a new option for us, and is actually the lowest cost, so we will continue to encourage our members to use that method whenever it's possible. Debit cards are the next most efficient, but we really can't pick and choose between credit or debit - but we're happy when we see more folks choosing to use debit versus credit.
At the end of the day, Sonic is a simple business: Our goal is to expand our fiber optic network reach, improving the performance and reliability of our services over the broadest possible area, reaching the most homes and businesses. Being as financially efficient as possible is part of the way we further those goals.