You can fill form 7 for anybody. When you try to fill form 7, it will ask you if it is for yourself or someone else. Click someone else and provide the relevant EPIC number to be cancelled.
Please note, there is no provision to upload any documents while submitting form 7. My first form 7 application was rejected stating that no documents were provided. I filled form 7 again and once I received acknowledgement number, I created a complaint/support ticket to specify that I want to remove my name but form7 doesn't have provision to upload files, I am attaching my surrender certificate to the support ticket along with the acknowledgement of form 7.
It worked out and my name was removed from electoral list successfully.