Bhutani Cyberthum - Assured Return Stopped

I recently bought a retail shop in Bhutani Cyberthum, and I’ve been receiving assured returns as per the agreement. However, last month, I only got the assured return for 15 days, and now they have completely stopped it. To make things worse, they sent me an email demanding the remaining payment, but they haven’t even provided a proper possession letter yet! It feels like they are trying to pressure me into paying without fulfilling their end of the deal.