Interest Payment towards delayed payment sent at the time of possession Under Construction

Hi, Have bought 2 BHK flat in March 2019 under construction project at Mira road JP Infra Hotcake 4 years no interest payment towards delayed payment sent by the builder .OC received in Oct 2022 and intimation for possession sent in Nov 2022 Have paid last installment dated 28th Dec 2022.Also other charges of Rs 3.8 lacs paid on 9th Feb 23 towards maintenance , society formation , utility etc Inspite of multiple calls and emails discussion no confirmation given to visit the flat or possession allotted On 15th March 23 received email stating interest of Rs 160121 is payable and possession will be given in 7 to 15 days No RM have asked for delayed payment earlier except for Rs 30000 in July 2022 due to multiple demands in 3 month .Also , asked for the latest developments so that can arrange and avoid delay in payment but no concrete information.However received demand for instalment every or alternate month (almost 10 demands in 12 months ) It is causing mental harassment.What should I do ?? Pls suggest