If you are a Facebook user you will get a very prompt reply.
I emailed Celebrity cruises stating my dissatisfaction for not going into St Petersburg, Russia. I thought it would have been a good PR exercise on Celebrity’s part to issue future cruise certificates. I copied the email to our TA, who replied the next day, to say that in her experience Celebrity take about 4 weeks to reply.
I put the same complaint on the Celebrity FB page and had a reply from Celebrity UK within 2 days.
I still haven’t had a reply to my e mail.