I did actually contact customer support by phone and it turns out there's a glitch in your software when trying to change the expiration date of the new credit card. The rep who helped me had never seen that problem previously. The old month was 8 and the new one is 11 but I could not get rid of the 8. I was able to change it to 1, then 2, but it would not go past 8. So I did it in reverse and changed it to 12, then 11 and it worked. Very weird.