Your job was complete, and finished, new job new contract, once you make the change without a new agreement, it puts you in a difficult position, getting legal advice was a good move.
We had a commercial account with a planned job, we installed as per dwg., just as you said, a month later, we are asked to re do the entire job, no problem we presented them with another contract, never heard from them again, and it was good we lost that account, because they go out to a different low bid contractor for every job.
