As per SEBI guidelines, a Demat account is required to buy/sell the shares, even if you are not taking delivery. Many brokers, including us, do not provide the facility of trading account alone. You would be required to open a Demat account as well. Moreover, AMC remains more or less the same, and now with the implementation of eDIS, your shares are secured. Hence, it is advisable to open a Demat account as well. Kindly refer to the link below-
Hope this helps!