How can you be charged a balance on a phone that was returned?

I was buying a I-phone.  Wal-mart rep said I could get a plan for about $60 a month for what I was paying.  After I purchased the phone, Wal-mart rep tried to set it up.  Called AT&T, but no they had to have the code.  When I signed up with AT&T numerous years ago, I didn't have to have a code.  So they sent me with the phone to the AT&T store, but no there the plan was about $75 a month and again they had to have the code  I had to drive 40 miles home, get on home internet to set a code to return the phone to Wal-mart and get my money back.  When I bought the phone, Walmart told me as long as I returned the phone in 14 days, there was no charge.  But oh yes, they didn't mention the restock fee of about $30.  But to make it more fun, when I received a bill, it included at $35.50 balance owed on the phone that I returned.  I contacted AT&T who assured me, the charges would be taken off.  This occurred 3 times - once after receiving a threatening letter regarding collection agency.  Then the last time I called, I got connected to the billing office who told me they didn't credit accounts that were no longer open.  So, basically I paid a restock fee and $35.50 for a phone I did not get.  I told the Billing Manager that fine, I would pay it and  would cancel my AT&T internet and direct TV.  Then when I went online to find out how to cancel these services, which I fully intend on doing as soon as the company I am transferring to can get them installed, the website would not tell me how to cancel.  Guess I will be on the phone another 10 hours arguing with AT&T.  Pretty sad given that I have been a loyal AT&T customer over 30 years, but no more - I'm done.