We hired a general contractor for a siding job. He is not listed through the BBB. In the original contract it only stipulates the removal and replacement of the siding, fascia, soffit, gutters and garage door frame. There is nothing listed about change orders. Now he is coming to us with these changes that he completed and is expecting payment. All he gave us was an invoice and never discussed cost or how he would handle a change if it came up. What do we do?