Identify the issues according to contract law (Consideration) raised by the following

Jay got a new Acme charge card because Acme advertised a low interest rate on unpaid balances. Jay transferred his balance from another credit card to the Acme card. After six months, Acme increased the rate and sent out a mailing that stated that, by continuing to use the card, the customer agreed to the rather significant change. Jay thought the mailing was just more junk mail and never read it. He continued to use the Acme card, paid the minimum payment for a couple of months, and after three months, finally noticed the change. The difference in the interest rate will cost Jay a substantial amount of money.