Good day I was selling my unit and we drafted an...

Good day I was selling my unit and we drafted an MOU signed by myself and buyer and he handed a guarantee cheaque to the agency and after the MOU date has expired the agency doesn't want to hand me the guarentee cheaque claiming that we have to open a RERA case despite there is a signed clause that if the buyer fails to do the transfer before or on the designated date I'm entitled for the guarentee cheaque as a penalty Please advice on the way forward