I used to work for a credit company that dealt with the applications for credit on SCS, another sofa company, purchases.
Many, many, many times we had phone calls and faxes telling us they wanted changes of the amount of credit required becase a customer has decided they wanted a different sofa, cheaper or more expensive. They seemed to be very good about it, and we easily changed the amount, since they were already accepted (though they did get credit search again, not good for the customer!)
Try and get your order changed, they ought to want to keep you happy!