"The card's bank would not approve a charge of this amount"

This message means the payment reached the customer's bank and the bank refused that amount. It is not a problem with your store or the customer's typing. The usual reasons are:

• a daily or per purchase spending limit on the card, very common on debit cards,
• a prepaid, gift or virtual card that cannot take a charge that size.

No money moved. Ask the customer to use a different card, or to call their bank to raise the limit and try again. Trying the same card again without that usually fails the same way.