Credit card company closed my account - how do I pay the least amount back possible?

I have several credit cards and I my largest I was carrying about $7k in debt. I was late on a payment in February, but other than that one time I had never been late or missed a payment with them. In April I got a notice that they decided to close my account. My living situation currently basically requires me to pay a bill, then use the card towards the end of the month to stay a float. So I made the probably horrible decision to stop paying on the closed account because it would eventually cause me to fall behind on my payments for my other cards.

Now my past due for them is about $700 with a balance of around $7.5k. I don't have a problem paying what I owe, I just want to pay as little as possible.

The company is Bank of America if it makes a difference. I receive calls from them probably 3 times a day, but never answer. I will be in a position to be able to start making a few hundred dollar payments a month starting in September.

Any advice?