"No, I don't."
"Yes, you do."
"I was billed this in error and am contesting this charge with my credit card company."
"The credit card company refused the charge and now we're trying to collect."
"Excuse me? I'm contesting the charge, and you need to take it up with the credit card company. I'll call them to find out what's going on, but you need to resolve it with them."
"Okay, sir, I will mark that down on your account, Thank you for using Sprint PCS."
"Not anymore. <click>"
So I call my credit card company.
"Hi, yes, I'm calling to find out the status of my contested charge to Sprint PCS."
"Hold on, I'll transfer you to contested charges. . . Hello?"
"Yes, I'm calling to find out the status of my contested charge."
"You haven't received a letter yet?"
"No, I have not."
"Okay, let me see. . . . Hmm, we sent a letter to Sprint, and they gave us a copy of the invoice. We said that's nice, but the whole point is that you're saying the invoice isn't valid, and that they need to establish that, and they haven't followed up on it."
"Well, they just called me trying to collect on this charge."
"There's nothing we can do about that, but we're not going to pay them until they can prove the charge was valid."
Since I contested the charge, Sprint decided to just come after me again than attempt to explain the situation to the credit card company (which they can't--the fundamental issue is that a customer service rep told me that I would receive no further charges on my credit card when I canceled and one came in after that point. They claim the charge is valid, I say they need to abide by what their reps tell people.) They'll probably take it to a collection agency. Last time that happened with a different company, I wrote a venomous letter to the collection agency explaining my position and did not hear from them again. I figure that might work this time. Worst case, Sprint gets less because the collection agency takes a cut (usually 50%). I think my credit rating can take a ding for $36.52 if necessary.
I have gone to the various anti-Sprint sites and customer complaint sites. There are many stories similar to mine, and Sprint has an order of magnitude more complaints than any cellular provider. Since I've switched to Verizon I've been able to call and be called almost all the time, which wasn't the case with Sprint, and my customer service experiences with Verizon have been incredibly positive (they charged my wife for Mobile Web, which we didn't want, and they credited us no questions asked.)
That's my story.