Nextel Filed report on my credit report, Internet

After reviewing my credit report, I found an item from Sprint Nextel on there.  They are saying I owe them some money.  I contacted the collection agency listed for them and they said they didn't have all the details, but that it was for an account that was only open for 3 months and that it seemed weird because it did not include any cancellation fees like they usually do.  I contacted Nextel, and they sent me forms, which I filled out sent in and they said I owed them money.  All they did was start sending me bills.  Only, I have NEVER had an account with them and they would not show me the information as to where the charges came from.  If teh charges came from me, then they could show me because it would have been personal information about ME.  Long story short, the amount still shows up on my credit report, despite the fact I have NEVER done business with them!!!