I just had the same experience you had. I was called about 7 times a day, 7 days a week. I knew i owed Citibank the money and i also asked for a payment plan and they refused saying i must come up with the money by 6 pm otherwise face legal action.
I explained to them that if i had all the money to pay it, i would have, and i wouldnt be in the situation to begin with.
They were very rude, one women even said to me "even the poor people in Puerto Rico pay their debt when we go after them, so if you wanted to pay it you would." First of all, I am Puerto Rican and i wanted to tell the women to "F" off.
i got off the phone with her and ignored the calls until i could think of a solution to come up with the money. I got another call this week by a man who said he has "no respect for me" because of my problem. So we argued and on the phone and i demaned to speak to a supervisor, who did nothing for me.
I panicked and thought of any way to come up with the money. I eventually asked my boss who's an attorney for the money and told him he could take it out of my paycheck. Being the wonderful person he is, he called the company on my behalf and they reduced my balance even more through his negotiation.
My advise to you, if you have a friend who is an attorney or any attorney you know that can call for you to negotiate the balance you owe, it will make a difference. If you are working maybe you can do what i do?? I know everyone's situations is different but i'm telling you at least i can sleep at night. Good Luck!