Visa extension from Shenzhen not allowed

Please, I need an urgent answer for this, I want to extend my L type for 30 days and I was just at the Exit and Entry Office in Luoho district and they refused to extend it unless I have a Chinese bank account with at least 20,000 RMB in it. Is it possible to extend from Hong Kong without such a request? Please let me know as my visa expires in seven days.. Many Thanks