Cognizant — Regarding IT Clearance and relieve letter

Hi, My Employee ID is 2185080. I left Cognitzant on 1 Dec 2022 and my asset pickup was done by vendor on 13 January 2023. I also mailed the acknowledgement slip to IT Clearance management. But I have not received any response from them. I called them and email them several times. But still no response. I also visited office but that the guy sitting there told me to send acknowledgement receipt. I told him I did it 5-6 times but no use. I had to return empty handed.. Im really frustrated now.. also unable to apply for the current opportunities... Please help me...!!