Taxation on NRO account

Hi all,

I have some savings in my Indian savings account accumulated from my monthly salary earnings.

I recently moved abroad and need to convert my savings account to NRO account. But once I do that, all interest on my savings will accrue 30% TDS.

I am not sure why my Indian savings accumulated from already taxed salary should now be taxed at 30% because of NRI status. Is there a legal way to avoid this taxation?

Thanks and Regards