After the bank card is bound to the mobile phone number, will it send a text message to the mobile phone when withdrawing money? What is the use of the reserved mobile phone number?

Yes Because the reserved mobile phone number is the information you left in the bank, and SMS is the mobile phone number you need to receive SMS reminders, the two are separate. So if the bank informs you of any business, it will send it to the reserved number, and the reminder business will be sent to your designated mobile phone number, so even if the reservation is changed, the SMS will still be sent to your previous mobile phone number.