Trying to get a seat assignment

When i tried to get a seat assignment online it was refused. However on the same site XLAirways will take my money for luggage charging $100+; saying no charge for carryon under a certain weight (not sure what that weight is cause it wasn't stated in pounds) even though i was transferred to the american version of the XLAirline site that took at least a minute). Anyway I cannot get a seat assignment, though i have already paid handsomely for a seat and frankly waiting until 2/3 days before flying ... well my experience is that most seats are already assigned by then. i don't understand this whole process. The planes are the same, the plane seating charts are the same but they will not make the seating charts available online to ME or allow ME a choice. i contacted Expedia who booked my flight and they sent a request to XLAirways for my seating choice. They too were surprised i could not book my seat. They also agreed my choices will be limited. You see i was traveling to France with a friend who had come to NY and I was returning to France with her (but not together on the 8+ hour flight). We planned to travel together. HAHA on us. Further the website that will not allow me to choose a seat said i have to pay an additional cost of at least twenty dollars for an aisle or window seat when i can actually request a seat wishing 2 to 3 days before my flight. What the Hell is going on? I don't understand who has priority on seating and why? I do know my flight was $200 more than my friend who booked from France. If I find myself in an uncomfortable seating and without my friend i will have no choice but to make everyone around me uncomfortable also; so much so that the XLAirways realizes this disregard toward their clients works both ways. So I have informed my friend that I won't request we sit together because i don't wish to embarrass her, and i doubt my effort to get us sitting together will come to anything. in closing: XLAIRWAYS: How dare you take my money for a seat on your plane, not give me an assigned seat and charge me for my choice within 2/3 days before the flight at which time my options are already limited. You are treating me like a caged animal for over 8 hours and charging me for it.