Yes, you can file RTI to The Telecom Regulatory Authority of India (TRAI). TRAI is a statutory body set up by the Government of India under section 3 of the Telecom Regulatory Authority of India Act, 1997.
Since its is a statutory body set up by the Government of India, therefore, it comes under the ambit of Section 2(h) of the RTI Act'2005 which has the definition of Public Authority. Hence, we can file RTI to TRAI.
To further know the procedure to file RTI to TRAI, you may visit the below mentioned link: