I'm also facing the same problem now, I purchased the holiday package since Sept'09, our trip will be in Nov'09. I tried to call them to book a seat and baggage, but for 2 months that I've been trying to call Go holiday no : 03-21719222 and 21719333 for that purpose, there is only answering machine and keep on holding the line.
I've even posted my complaint on their website twice, yes they did replied me by email and advised me that they have informed Go Holiday and some one will call me soon, however it's been 10days, no one call me till now!
Very frustrated, as I'm bringing my children for the trip, I need to book seats so that we all can sit together. And not only that, it'll cost lesser to pre-buy baggage than to buy it during check in.