When that has happened to me I call CS and have them process the payment. This way only that one easy pay is sent through. On HSN you can go online and pay for each flex pay at a time. Sometimes I will pay a flex pay early. But on QVC, they don't seem to be set up like that. They want you to pay the entire amount. So that is why I always call.
And if you do update your new expiration date on your account, if you have any waitlist items or auto-delivery items, those don't get updated with your date. I've had to go into AD and change that myself. QVC can update all easy pays for you at once with the new expiration date but for some reason waitlist and AD items I've had to do myself.