I made my reservation using two Cat 1-4 certificates on MR website. When I review my reservation, I found I made one little mistake. I should put 2 as number of guests instead of 1. Though I didn't know if that matters, I decided to call reservation center to correct that. The agent helped me to correct that but the rest conversation made me more confused. She claimed that I cannot make my reservation online using free night certificate. I pointed out that I already made my reservation and the reservation did show that two certificates attached. But she hold her position firmly and offered to do it manually again. After her help, I couldn't see any difference (other than the number of guest as I requested) before and after.
So, the question is, is she correct that I have to call reservation center to use free night certificate?