[gommm]

I would take the "you feel that way" out and replace it by:

"I'm sorry with our miscommunication, let us refund you your money. However, we've developed some great premium features that you may be interested in; and of course our the main features are free. Can we convince you otherwise?"

"I'm sorry you feel that way" makes it seems that it's the customer's fault and not their fault, it's demeaning to the customer.