You probably need to use a travel agent. You can try an online travel agent, but may be tricky to make sure you get the M/U fares you need -- you can start my asking for only refundable fares, but that might bump you to Y. Perhaps others can post of the their successes. Probably not a great idea to call AC directly though, or they may find a way to kill this deal. Others may feel that we shouldn't even be discussing it here.