Cognizant — turnaround time for the issuance of employment letter

I have applied for issue of employement letter for my visa application. It has been more than 20days and i have not received any response from them despite of multiple reminders and reiteration about importance of deadline. This is not at all expected from an iso certified company like cognizant. I believe that last communication from hr team indicated the request is pending at previous supervisor. I believe she is reluctant to approve the letter.