Disputed Charge will NOT be taken care of!!!! HELP!

Let me start off by saying I have 10 lines with Att, and we've been with this company for several years. We've been out of contract for almost 2 years, and due to the tremendous problems I am having with this charge on my account, I am seriously considering changing providers.

The problem:

In June 2016 one of the 10 lines had a problem with their phone. We have the insurance purchased on our account, so we just requested a phone replacement for that phone (LG G3). 

It came a couple days later in the mail, except I wasn't there to receive it. My mom got diagnosed with Leukemia at this same time, and was immediately put into the hospital. I was staying with my mom in the hospital for her 30 day Induction and didn't even see the package until a couple weeks after it had arrived. I called At&t and let them know I would be sending it in late, as I only had 10 days to return the defective device, the girl that answered said it was no problem and that she would note the account. I also noticed the return shipping label was not in the box, so she sent me a new one so I could send the device back. 

I sent it back on July 2, 2016, and have the tracking number of the sent package. I noticed a couple weeks later when looking at my bill that I had been charged 774.00 for the phone that "wasn't returned". I called immediately and they said they couldn't remove it because it was sent in late. I explained the situation and told them how I had called to let them know the phone was going to be late, and that there should be a note about it. I don't actually know if the first girl noted the account, cause the agent I was speaking to went ahead and transferred me to a manager. This manager was wonderful and helpful and stayed on the line with me as he verified the phone was received and then once, we got disconnected, and he called me right back. He said he'd get the credit back on the account so I wouldn't have to pay the 774.00, and gave me his credentials so I could check back on it if there was any problems.

There were problems. He had said it would take until the next Thurs to get the charge removed, so I looked on Thurs and it had not been removed. I called again, gave the rep the manager's credentials to see if I could speak directly to him. I guess that doesn't work that way, but the rep tried her best to help. She ended up transferring me around to another person who, after verifying that they actually received the phone back in July, said she would "email" her manager and that the issue should be resolved by the 25th of August. She also pushed my phone bill out to be due then as well so I could pay the bill after the 774 was removed. Aug 25 came around and the 774 was still on there. I called again.

This new agent said that it looked like the previous agent had intended to put the 774 into dispute but hadn't actually done it, so the new agent was doing that, and she was escalating it so it would be resolved quickly as this was nearly 2 mos after the first call. I told her that I would like to pay my normal bill and that way my bill wouldn't continue to increase. She said to pay all except the 774 and everything else would be in dispute so the phones would not be shut off. I paid the 493 that was remaining, and 3-4 days later, the phones were shut off. 

I called At&t a little panicky because my mom is in a hospital in a different city getting treatment and I have no cell phone, so they looked through the notes, saw that the 774 is in dispute and turned the phones back on. I was very grateful! When I asked about the progress of the dispute they had no additional information, but the girl told me that her manager would call me within 4 business days, which was the following Thursday as this was a Friday. 

Thursday came and went, and I forgot to call as I was in the hospital in the new city with my mom. I remembered on Monday and called At&t. I spoke to an agent that said they could see all the notes on the account and that they would transfer to a manager. I waited on hold for over an hour, then got disconnected. I was livid, but decided I'd call again the next day. 

I called again yesterday and spoke to a guy who said he was the person I needed to speak to. This was after asking immediately to speak to a supervisor, him going through the, "oh of course I'll transfer you to a supervisor, but can I know the problem first?". After he said he could help, I again stayed on the phone for 29 mins and then abruptly was transferred with no notice back to the automated help system. I pressed the 0 to speak to a rep again and waited again. I got a new girl who I asked immediately if I could speak to her supervisor. She asked why and I told her again, and she said she understood why I needed a supervisor and then transferred me to Uverse. 

The people at Uverse had no idea why she transferred me to them because while my DirectTV bill and At&t bill are combined, the credit has to come from the At&t side (whatever that means, they're supposedly working together). She explained that she could do nothing for me but that she was going to transfer me to a manager on the Mobility side and explain the situation and then transfer me through.

Instead she transferred me back to the automated system where I pressed the 0 button again to speak to a rep. I got a new girl, who said that she would not transfer me again. She promised that if we got disconnected she'd call right back, and she was going to do all the research with me on the phone. I hoped she was for real. 

After almost 2 hrs she comes back on the line (she had come back on the line to ask questions and make sure I knew she was still there throughout the whole call), to tell me that she couldn't verify the phone was ever received. This was the first time I'd heard this. Every other time they'd tried to verify the phone was received, they verified it. I also had the tracking number, so I gave that to her so she could look it up that way. I asked her if I would be liable for the phone if the tracking number showed that I shipped it, the post office received it, but then it didn't get delivered. She said she didn't know but she'd find out.

After waiting a few more minutes, I got a shock of the automated system asking me if I wanted to speak to a representative, or the other options. 

I was so angry I had to hang up and go breathe in a corner. 

Then I got onto the At&t website and started a chat with an agent. I told her the situation, asked for a manager to call me, and she verified once again that they received the phone and I was very relieved when she said she could see it was returned in July. She said she'd get a manager to join the chat, she did, then she left the chat and the manager introduced himself then the chat froze, or stopped working. I think it was because I was logged out of the website due to inactivity. I wasn't using the website, I was talking to the agent so the page timed out. 

I am at a loss. I am so angry and frustrated and I need to get this matter resolved. 

I am filing a complaint and thought this is my last ditch effort to resolve this before going there. I will attach the tracking information and I have notes of almost all my calls into At&t, so if you need names of agents or managers, I probably have them. [edited for privacy – please do not post personal information]