I'd like to answer this positively but I can't. I have found Olsen's phone reservations very difficult to deal with. When I tried to book a back-to-back well in advance they wouldn't even deduct the unused airfares and a letter of complaint went unanswered. I have just had their Christmas brochure; tried to book, but was told cabin would beallocated on arrival - NOT in the brochure. Normally you should get a reduction for unused airfare and a discount on the second cruise, but- - - - - - - - .
Best option is contact a reliable travel agent and let them sort out these problems. If you don't know of one I have been using Victoria Travel since 1999 their prices are good and they are the main booking agent for some of the big cruise lines. The call is free 0800 091 162.
Always use a Travel Agent. You will get a better price from them because the cruise companies give them commission which they pass on to their clients. The company I use is The Cruise Line and their telephone number is 0800 008 6677. I've booked a back to back with them and I'm off to the Caribbean in 2 weeks on NCL's Pearl.