The information provided by you is not sufficient for anyone to guide. Can you enclose the terms of your bond? It might help others to advise properly. Based on the info furnished, any bond has a value attached to it. If it is mentioned that the original certificate shall stay with them for the specified duration, there must be a clause stating the penalty attached for breaching this agreement.
Read your bond paper (if you have a copy) or ask your HR/Management to provide one. If you agree to pay that penalty amount, they'll return the certificates (assuming you are not continuing your duties with the company after that). I suggest you provide detailed correct information.
Regards,
Hiral