Investment firm not paying investors as promised

An investment firm promised to pay investor 9% interest with the interest being paid monthly.
When the investor first invested in February 2023, the interest was being paid on time monthly, though the principal was not refunded on February 2024 as promised.
Since the sales people were very persistent the investor made another investment in January 2024, which again promised 9% monthly interest.
However, the investment firm has not credited the interest on February 9, March 9.
When the investor visited the office, the staff was evasive
Now the investor will have to waste time and office, visiting the office to get the principal or interest.
Though the office is very posh, they are not paying even a small amount of Rs 150 as monthly interest to the investor.