DOTEL/R/2017/80415

Hi,
My number is 8880170670 initially my network was Reliance on Feb 2017, I have ported out to Airtel.
I needed call data from September-2016 to December-2016 because I have to submit it to court but reliance people replied that they cannot provide CDR as I have ported out to Airtel. But I asked just 10 months back call data, how can they remove all data immediately after porting out....
I want to know how many years telecom companies need to store call data as per TRAI regulations.
thank you,
Swapna Jangam.