Why is there a demand to change a few words of National Anthem?

West Bengal Chief Minister Mamata Banerjee has challenged the Bharatiya Janata Party to change the national anthem. She said this in the context of a letter written by MP Subramanian Swamy to Prime Minister Narendra Modi. Swami has also shared this letter sent to PM Modi on Twitter. 'Jana Gana Mana ..' was first sung on 27 December 1911. This song was written in Bengali by Rabindranath Tagore. The Constituent Assembly adopted the Hindi version of Jana Gana Mana on 24 January 1950 as the national anthem of India.