Blowing-off steam...Never blow off steam at underlings. They're usually minimun wage phone jockeys who have no power, know nothing, and can't personally help you. Keep asking for a supervisor or manager, go as far up the chain of command as you can get, if you have to. Always ask for everybody's name and write them down. Keep your cool and keep on point. Make them squirm, keep reminding them that this is their problem and asking what THEY are going to do about it and how they are going to make up for your lost time and money? Be polite to those who actually do help you.
If you still do not get a satisfactory solution, write a letter to the head of the company. Detailing your time spent, detailing the answers and run-arounds you got from each individual. Praise those who actually helped; be specific about those who didn't. Detail the mouth-breathers' rudeness, casualness, helplessness. Intimate that you expect some form of compensation for your wasted time and trouble resolving this.
Make the letter witty or acerbicly witty, if need be...but definitely let the top dogs know that you are disatisfied with their service. It always helps to enclose such phrases, "I was really looking forward to such and so and had heard such good things about your company. How disappointed I was." The old jockeying praise with complaint ploy. "I don't how such a fine company could condone such poor service." "I thought I should bring this appalling situation to your attention as I'm sure you are not aware of how your company is being represented in the field."
Always a litany of dates and times and what happened specifically with each individual is important. Blame those who deserve it; praise those who deserve it. Don't vent in a tirade or just spew invectives. Be creative and amusing in your criticism.
The more intelligent and collected your comments are, the more your complaint will be paid attention to. Searing satire leavened with a heaping dose of sardonic, incisive humour is always more effective than a flailing scream-fest where you just call everybody an asshole.
Usually, the classier the company, the better the results. Once Virgin Airways was late sending us our tickets. They finally came before our trip. But not before I had written them a rather long witty, entertaining letter, telling them how much I enjoyed their airline and how I'm sure this was some sort of aberration in their usually excellent service and giving them a humourously exasperated account of employees (by name), excuses, misinformation, conflicting information I had received in trying to facilitate the problem. This resulted in an apologetic phone call and getting a seventy-five dollar voucher for duty-free items on the plane (or maybe we could just take the cash). The point was they accommodated us for our trouble. (I was angling for a bump up to Upper Class, but alas...).
Be polite, but firm, and witty. Stern and unyielding, if need be. But once you scream, you've lost the upper hand.
If none of the above works, crank up the CD player, crawl in a fetal ball, and fortify yourself with lots of potato chips, chocolate, and other comfort foods.