Check your contract to see if it has a clause pertaining to currency conversion of RMB to foreign currency. Then ask your FAO to assist you in this matter. He should know the regulations. If he doesn't, he can find out on your behalf. Then you and he can go to the bank together to deal with the matter.
In some provincial capitals, there are black marketeers hanging around outside the branch that is frequented by foreign tourists. Probably they are also operating in the capital and in municipalities too. They are usually standing next to their motorcycles in the bank car park. Walk near them, and they'll address you. Not that I've ever used them, but it's an option if all else fails!