Another reservation linking question!
 

We have a 14 night June stay at CSR booked via a travel agent. Norwegian then cancelled our flight and booked us on to a flight the day before. I have therefore booked 1 further night at CSR but via Agoda (at a great price). So, I have 2 separate reservations at CSR one for 1 night and one for 14 nights. I would obviously much rather have the same room for the entire 15 night stay. What is the best way to achieve that linkage? Thanks!