AT&T Cellular Service Cingular Billing Issue that they did not find for 3 months and expected me to pay ASAP Carol Stream, Illinois

Billing issue. Posted payment for 3-mos.to incorrect bank acct. that was closed in 2007 and did not notify me until 6/2/2012. They wanted $641.98 by 6/22/2012 or they were going to disconnect our service. It took them 3 mos. to find their error and they were giving me 10 days to come up with the pmt for all 3-months. I admit that I should have caught it as well since the money did not come out of my current account that they have on file but my bill was correct since they did not catch it until 5/20/2012 and notified me on 6/2/2012. They were able to reverse the incorrect payment for May to the correct bank accoutn that I have been using for 5 years but they still wanted me to pay for 3 months of payments. Our bill was $214.67 per month and I couldn't possibly come up with $641 in 10-days. They wanted March and April plus current bill which came to that huge amount. When I tried to get them to work with me and make payment arrangements, they sadi they could only go 7 days out for arrangements. I asked for supervisors and than managers and none of them would help. I just made payment arrangements to buy me some time while I researched other providers and than when I got new service with another carrier, I told them I couldn't pay that much money and my account was canceled. The other 2 phone lines on my account were still active until after the 20th since the arrangement was made for that far out but when I got my new sim card for my phone line on 6/7/2012, my phone line cxled automatially. I have been with AT&T for many years and loved their service but when they wouldn't work with me (and I mean wouldn't not couldn't) I had no choice but to cxl. They could have helped me out by arranging to let me pay an extra $50 or $60 per month until it was paid but they wouldn't and it was their error and they expected me to suffer & pay the consequences for their mistake. I know from now on, I am going to follow my bank acct. more carefully. I am getting a bit older and forgetful which is probably why I didn't question it, especially since my bills were correct and showed the payments posted. They reversed all of them on 6/1/2012 and notified me with an automated phone message on 6/2/2012. They couldn't even give me the courtesy of speaking with a live person. Well, now I am with a different company and couldn't be happier. My daughter & son-in-law sitll haven'tselected a new provider and since they were onmy AT&T acct. theirs was disconnected on the 22nd of June because they saw no payments as promised.  I suppose they are so big now that they don't care about their customers anymore and if it weren't for customers they wouldn't have a paycheck.