This was already happened to me as well and But When the customer ask me to do more then I send him the custom offer and he said he want this work in the same price, And I told him that I already mentioned in my gig that this particular package will have this work only, he refuse. I contact fiverr support and they read the convo and saw my gig. They found that I was telling the right thing.
They canceled the order and My stats doesn't get any affect.
Whenever you face any issue, Just contact support.