Jenkva

I am scheduled to cruise on a 4 day cruise to Cozumel from New Orleans. I called carnival to try to move my cruise a month later ( same destination/ same length/same port) due to Omicron concerns, they want to charge me $204 more "because I got a deal when I booked". Thar makes no sense to me since I am trying to avoid canceling all together and requesting a refund. Is this right?