Delhi Police — extra amount demanding after challan payment

Address:

Delhi Police, 110092

Dear sir,
I have already paid an amt of 4000 for challan number - dl[protected] issued to me for traffic violation..
But when i consulted to the concerned for taking return my rc & dl after challan payment then they are demanding again 4000 in addition to the paid challan amt & denied to return my dl & rc..
However i have already paid 4000 for the issued challan to me then why is it so & why they demanding again..
Required your kind help in this concern on very urgent basis..

Regards