Product: Mortgage

Flagstar Bank received my mortgage from XXXX on XX/XX/XXXX. I received letters from Flagstar on XX/XX/XXXX, dated XX/XX/XXXX, stating they are accelerating the foreclosure process and I had to pay all the back payments, I was behind since XX/XX/XXXX, totaling {$5100.00} by XX/XX/XXXX, to keep my home. They gave me two weeks. 
I called on XX/XX/XXXX and spoke to a rep that stated I was in danger of foreclosure but could apply for mortgage assistance, said she sent a packet. I then asked her why the amount that XXXX sent me, {$140000.00}, was different than what they said, over {$140000.00}. She said it was because of my late payments ; I said no, that's a double payment. She argued with me for a bit, I asked for her supervisor, she hung up on me. I called back and spoke to another rep, rude, and condescending, he explained the mortgage part to me, I kept telling him I knew that part, I needed him to explain the dollar discrepancies. He said, I can't we are closing now, I said, no, you guys aren't according to your letters and website, and he said yep, call again tomorrow, I said no, I want to dispute this then. He said ok, let me give you the address, and hung up on me. 
I called XX/XX/XXXX, spoke to a rep and he said I could fax a dispute in, I asked him what the difference in money was and he didn't know, he had to transfer me to customer service. The customer service rep pulled my loan up, said ohhhh, I have to transfer you, and sent me back to the beginning of the automated line, without even asking what I needed. It was a bank branch, who then sent me to a different department, where the rep refused to tell me what the charges were. She said I could send in a dispute, she didn't tell me how, but that it was for Flagstar to know, not me, and that they would look at it and determine if it was correct. I asked for her manager and she told me no immediately, I then asked for her team lead and she sent me to her. The team lead then told me the charges were my late payments. I said so I pay the late payments on top of the monthly payments in the original loan, which is a double payment? She said it just sounds like I am saying I don't owe it. This was after she argued with me. I asked her then, did XXXX send that over, and she wouldn't answer me, she kept trying to put the blame on me not paying, saying this was because I haven't paid my bills. I kept saying who's charge is this, she finally said it is XXXX, they sent over the {$5100.00} in addition to the loan, and if someone calls when I sell my house my payoff amount will be well over {$140000.00}. 
I was not advised on my first two calls how to dispute, I still have not been given a full explanation on the date, two weeks is not enough time for over {$5000.00}. I have told them I am putting my house on the market to sell it, and they keep saying it is going to go to foreclosure. 
The dollar figure needs to be fixed, I can't and shouldn't have to pay double payments. I shouldn't be treated poorly or hung up on simply because I am in a tight spot financially right now. 
Lastly, they are preying on people that they think they can bully, by being in a position of default payments, they feel they can say foreclosure and charge all this extra money without question. They have cost me approximately 2 1/2 hours worth of work, simply through argument and stalling tactics. The request for managers to call me back did not work, no manager has ever spoke to me about this. I don't believe the reps even put the requests in.