You have to mention the PAN which you are using currently on top of the application form. All other PAN/s inadvertently allotted to you should be mentioned at item no. 10 and the corresponding PAN card(s) should be submitted for cancellation along with the form.
The charges for applying for PAN online at NSDL-TIN website are the same as that for applying for PAN through TIN-FCs; i.e. 93 + service tax. If address for communication is a foreign address, the fee payable is 971.00 (including service tax).