First, I gotta agree with the posters above who point out that raising one's voice, complaining loudly, etc., to a telephone Customer Service Rep is unnecessary. This person did NOT make the changes or set the policies or sell out the item after your order was finalized but before it was selected/shipped... CSRs are all human beings, just like us. They'll do what they can
This is a critical point. Arguing with or generally making trouble for the person in the best position to help you isn't a good plan.
No airline is "supposed" to buy Delta. US Airways has made an offer, and is not backing down - but do you REALLY want an airline monopoly (which it appears is US Airlines' goal - given that they already purchased America West and codeshare with United
US Airways goal is to reach a sustainable size. Smaller airlines won't survive in this insanely competitive and low-margin industry, unless they radically reduce the number of cities they serve, aiming at only the most profitable cities (which will really mess up smaller cities that rely on these airlines for service or for affordable service).
Industry experts are clear: There are simply too many airlines. Who pays for that imbalance? So far, we all have, as our taxes have been used to prop-up failing airlines, and in some cases we taxpayers have even assumed their pension liabilities. It is not in the taxpayer's best interest to have so many airlines, to have such a competitive environment, to have such a low-margin industry. And I'm a taxpayer much more than I'm an airline passenger!
As it is, it isn't clear to me if US Airways took over America West or America West took over US Airways. It was as even a merger as we've seen in the airline industry in decades -- two airlines coming together because alone they wouldn't have survived. The code-share with United doesn't constitute much of anything, really (especially in terms of accusations such as "monopoly"), and if anything, United has the upper-hand in that relationship. Furthermore, a Delta-US Airways merger would bring an end to the United code-share agreement.
In the end, there is probably enough room for about five or six major airlines (over 30 million passengers per year) in the United States: American, United, Delta (with or without US Airways) and Southwest, for sure. So that leaves one or two slots for Northwest, US Airways, and Continental. And give it time, and airlines like JetBlue and AirTran will make the situation even murkier. Something has got to give.