How Can I Prove My Experience with Company A When My Letter Only Mentions a Third Party?

Dear Sir,

I am working on third-party payroll in Company A. At the time of joining, the company gave me an appointment letter for the third party. Now, I have obtained a new job on the company's payroll, and I require an experience certificate. However, the company provided me with an experience letter on the third party's letterhead without mentioning the company name. The new company requires documentation to confirm that I worked with Company A. What should I do?

Thank you.

How about payslips, salary credited by the company's name, any physical documents on which your name as well as the company name is specified. You can also provide your HR contact details for verification.

Dear Mr. Raviprasad,

Try to get someone senior from your ex-company to endorse your skills, refer you, or congratulate you on your new job.

Hope this works.