Since SIM card at Pudong International Airport is so expensive, I'm going to purchase a SIM card at local branches in China/Shanghai. I consider either China Unicom or China Mobile, though the latter might not be available to my phone due to different frequencies (so I prefer China Unicom).
However, because I don't have cash, I have to purchase it using a credit card (either Amex or Visa, and not UnionPay). I must definitely avoid the case of failing to purchase it, since it is so essential for a 15-day stay.
So I have to make sure that I can purchase it with certainty. Can I purchase it using a credit card in these branches?