My AirPod pro has crackling noise issue and been purchased in march 2020 but service person saying mine is ineligible for AirPod pro service program

Refer to this document AirPods Pro Service Program for Sound Issues - Apple Support

It says, "The program covers affected AirPods Pro for 3 years after the first retail sale of the unit."

If you bought yours in March of 2020 then you are now 2-3 months past the date window.

Refer to this document for ways to contact Apple --> Choose your country or region - Official Apple Support

Select your country (also look for "other" regions), then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.

or:

Contact Apple for support and service by telephone --> Contact Apple for support and service - Apple Support

Have them sort it out with the service center which I presume is an Apple authorized service location? Alternatively, send them to Apple itself since they are in agreement with you. AirPods Repair & Service - Apple Support