I too have been a customer or rather of a victim of Sprint / Nextel Corporation. All of the same noted issues. Billing problems, technical issues, contractual problems, and customer service problems. I won't detail the events because it is too time consuming and I don't think any of us need to hear the specific amounts of time and money that have extorted to date.
What I can say is due to my frustration of dealing with the Sprint method of customer service support, I realized at one point that no matter how many times I called in, rationally requested senior level assistance, attempted backdoor type of calls seeking any other department than the one I had before, I was not going to gain the assistance that was needed to correct these problems.
As many of you are professionals and work in large companies, you are aware of the fact that publicly traded companies always have a Board of Directors and are required to act on the behalf of their investors. In that, there is ALWAYS someone that with a little bit of research will be the correct contact person for results.
After a little research I used some common sense, and looked up the names Board of Directors, and the President of the company. I then looked that the email address format that was used in the contact section of the marketing department and followed the format to then send my complaints and requests to the President and the entire board.
This produced results. I began receiving calls from senior level members of management at the corporate office and soon my issues were temporarily resolved. More issues have arouse over the course of 9 months, but each time it does, I simply send a informative, rational, email to the president of Sprint / Nextel and within that day I have someone calling me, asking me what they can do for me rather than me chasing them around.
If you really want results, I suggest following the same process. Just remember that if and when you do write any of these contacts, your point is to actually resolve your issues. Sending emails of a threatening nature, screaming, yelling, or slamming them with demands will only end up with someone possibly deleting your email without taking your needs into consideration.
I am not suggesting that you are to suck up or please for assistance. It is their job to assist their customers regardless of the position they hold within the company. Every employee within Sprint / Nextel is only employed because we as customers choose to pay for the services that they can offer. I am however, stating the obvious in that if I were to receive thousands of emails all in a hostel nature, the actual problem you were writing about would be clouded and hard for me to continue to take the time and read each and every email.
Like I said this is just a suggestion as a method to correct problems that may be occurring, it may not have the same results as it did for me. It can't hurt to try.