Is it necessary to open SMS to remind ICBC of electronic payment?

That's not true. The SMS reminder you mentioned should be a reminder of balance change, and the bank will send you a text message after saving money and withdrawing money.

When opening ICBC e-payment, you don't need to open the balance change reminder at the same time, you need to use the mobile phone number to receive the verification code, so you generally need to use the mobile phone number reserved at the counter to open it. If you log in to online banking, you can use any mobile phone number, so there is no limit.