This just happened to me this weekend. My husband received the email from FBC on Saturday. It provided very little detail. On Sunday morning, Delta sent us both emails saying our flights had changed. The flight to the cruise was a small change, but our return flight was a problem. Originally, we were supposed to fly home at 5:50pm, and it got moved to 9:40am! There's no way we could make it from the ship to the airport on time. I checked my Celebrity account, and the old flights were still listed. So, I decided to call and work it all out. FBC requested Delta put us on a later flight. The rep said it can take up to 10 business days to process but that it usually happens sooner. She suggested I call back in on Thursday or Friday of this week if I haven't heard anything from Delta.
I would suggest looking up your reservation through your airline. This will let you see the actual change. If you don't like it, call FBC.