Cancelation fee for WHAT

In August my friends and I decided to go on a cruise in November, so we phoned Imagine Cruising since they were cheaper when we compared the price to MSC. We were told about a deposit of R3000 for 4. After a couple of weeks we put the money together and confirmed the booking, then we were told to settle the balance by the end of September. Came the end of September my 2 friends decided to pull out as more pressing issues came up. Myself and the remaining friend decided to still go ahead with the booking, but to our surprise we were told that we were still going to pay for 4 as a penalty and to cancel the 2 friends that pulled out we'd have to pay around R1000 per person. Since this holiday was now going to cost my friend and I an arm and leg we also decided to cancel. We thought that would be the end of it, we would forfeit the R3000 deposit and move on with our lives. Now I get an email stating that we would be liable for a cancelation penalty. This doesn't make sense at all. Annoyed and unhappy with this money hungry agency. By the way my friend and I decided to book via MSC directly they were cheaper this time around and we'll be on the cruise.