I own a flooring company in NC. I have a customer that isn’t paying his balance. He paid 1/2 down and still owes close to 5k. Work was completed properly and after so we requested payment of balance. The customer then told me he wanted the floors the same height as his existing floor which is hardwood and the new floor being LVT. This was never discussed and I had the customer sign off on the estimate that states there will be transitions between old and new floor. The balance is well over 30 days behind. What can I do?