Hello guys, I also worked in TCS for 3 years. I started approaching TCS HR on June2016. Then I approached my team lead to send an email regarding the letter to HR. HR didn't consider it. Approached my project lead luckily who got promoted to Group lead position. He requested them to provide the skill certificate. Then his email sent to ISU head or corporate head. They accepted because it came from Group lead. Finally, I got the skill letter in TCS format on Sep 2016. But the letter didn't mention information such as number of hours/week, and all designations during my tenure . As a proof, I attached the emails from the HR for missing details requested by CIC, relieving letter, Pay slips copies, and skill letter.
Try to contact your Project lead or Group lead or ISU head. But only Group lead or ISU head has the authority to approve it.
Hope this helps you.