DHL Express India — Address proof rejected multiple times

Hi sir this is to inform you that i have studied online course and the education originl certificate is arriving from usa. The dhl asked for address proof..i submit the pg address proof the rent, receipt, electricity bill.. Everything is been rejected. They are asking to stamp on the receipt.. I ask pg owner but they dont have a stamp.. I am very worried my original certificate is with dhl.. If they will not give my certificate they will destroy my future. I am feeling hopeless and helpless... My tracking number is [protected]