Failure to disclose full cost

I booked a Mediterranean Cruise with Imagine Cruises and the sales representative was very happy to tell me just how cheap it was. I booked Aug/Sept and had to pay in full by 15 December 2014 for my May departure. When I received final confirmation I enquired about any other costs and was assured all was paid for. Two days prior to departure Costa cruises sends a letter advising that a EUR150 had to be paid into the Costa card or a credit card has to be registered. In addition at the end of the cruise 18 May 2015, an amount of EUR59.50 per person was added to the accounts of all the South Africans on board - a hotel service fee according to Costa Customer Services. When the amount was queried we were informed that our SA agent was aware of the cost and should have advised accordingly. Curiously, the Spaniards on board were not liable for the so - called service fee.