Indian Post Department — not accepting valid currency of 500 rs.

Address: Gandhinagar, Gujarat

I am right now at post office for submitting m.com form for which i have to pay 950 rs. As i given indian currency of 500rs they denied to take currency stating that there is something written on your currency
I told him to give me in writing that you will not accept money for what reason but he is denying for doing that
Person responsible for that is
Gaurav shah
Postal asistant officer.