Usually you don't get a choice of upgrades. It sounds like they offered you an upgrade but you turned it down. They are not going to keep coming to you until you find one to your liking. Upgrades are usually to a similar cabin on a higher deck; but the location may actually be less desirable, like near an elevator or laundry room.
Once onboard there is not much chance of an upgrade as the ships usually sail full. I fail to see where turning down their offer entitles you to any compensation.