GoldPremier,

I wouldnt make an issue of this. You are violating all sorts of Continental rules by not using the return portions of these tickets ("throw away tickets").

It is odd how many different answers that you have received here. My answer would be that within the rules of the original fare ticket (could be 2 weeks, 30 days, etc.) you can change the return flight for $75 (booked in the same class of service). You do not have to pay the difference in price. The only time that the difference in price comes up is when you don't use any portion of the ticket and you need to buy a completely new ticket.