Having a client, who refuses to pay for the change orders. Now I'm short on money to finish the original contract.
You should consider preparing a letter to mail by certified mail, return receipt requested, to the customer to set out the facts and to demand the relief that you want. Attach the change orders at issue, and if you have performed the work, attach photographs of the completed work. Make sure that your letter is professional and business like as it may be evidence later.
If need be, consider filing suit in small claims court (assuming that your claim is less than $20,000), using your letter as evidence.
Good luck.