Depends on how much USD u plan to send . Usually riatransfer( good rates small amounts) and moneygram ,XE.com are also good and trustworthy.
Just dont go with some untrusted name .
If u plan to do large amounts 50k USD then best is Wise (formerly known as Transferwise)
Transfer from ur acc to NRE (exempted) and if u plan to give to parents then u can do that its tax free for them . As long ur under 250kUSD i think , gifts are non taxable.
Charges depends on several factors , some will give u exact rate but charge fees ef Wise , some will give u bad exchange rate but no transfer fees . Hence check that acordingly .