Anytime I call a company, any company, with am issue I try to remember that it is another human being on the other end.
If I cannot get my issue resolved with the lower tier I ask, do not demand, to speak to someone higher on the chain of command than the person I'm speaking to.
If I cannot get my issue resolved, after going as high as I can on the call, I send an e-mail to the highest ranking person in the company that I can scrounge an e-mail address for.
I never yell, I never curse, I never demand.
It seems to work for me. I am rarely refused and even in my e-mails I am concise, consistent, and polite.
My strategy as well.
I'd also add: be reasonable, be persistent, and (most importantly) keep notes. Get their name, record the date, time, and summary of your phone call. It's amazing how fast you can cut through the B.S. on the other end when you say to them: "I called on June 5th around noon and spoke with Nancy in regards to this issue..." Gives them very little wiggle room as they know that your records match theirs and they can't try to brush you off.