Ok Fair enough, but that is not a good situation to be in.
Is the client being charged for the changes, if not, then the company need to set a standard form of contract or even an email, saying 2 changes and then charged per hour after the fact.
It's not good for you either, the stress will have a bad effect over time, and it's not your fault.
Seriously , your all being screwed when this happens, and it happens to us all.
get set up by all means , but you should not be paying for it, financially or stress wise.