In Pennsylvania, the client's file is the client's property and you have an absolute right to your records. It may be as simple as telephoning the office and asking for your file. If that does not work you ought to write your attorney a letter clearly requesting the file, which you should send via regualr U.S. mail and return receipt requested so you have documentary evidence that you requested the same. Depending on the language of your orignal retainer agreement though, you may be responsible for costs that your attorney had laid out on your behalf so be sure to read your retainer carefully.
Please note the baove answer does not constitute legal advice and you should consult with an attorney and act on the advice of counse.
The file belongs to you. Make it clear to him that you will take it to the next step, i.e., bar complaint (it is one of the most frequent bar complaints), if he doesn't turn file over within a couple days.