The characters in the slums of Kolkata (then known as Calcutta) pronounced their names in the Hindi way (when speaking in English) and in the Bengali way (when speaking in Bengali). (e.g. Kavitha is pronounced more like Kobita in Bengali)
Characters referred to Bangladesh during scenes taking place in 1949 - right after the partition. Bangladesh ought to have been referred to as East Pakistan. The name Bangladesh didn't come into usage until many years later when East Pakistan started thinking about Independence. (And it was only after independence in 1971 that it became officially known as Bangladesh.)