I am an American in Mongolia and I applied for a Chinese visa in America through a travel documents company before my trip here. They accidentally only put one entry allowed for China. I am traveling back through China and staying in China for a week on the way back to the U.S. and I realized that I no longer have a valid visa (because my visa was used during my layover on the way to Mongolia). Is there a quick solution to getting this visa issue fixed? I leave on the 11th of August.