I have been disputing and fighting AES for two years because of late payments that were added to my credit report during a back dated forbearance and finally won! History: I requested a back dated forbearance which would cover the dates of the late payments and AES granted me the forbearance with a letter stating it would be back dated. However, they did not remove the late payments from my credit report. After numerous calls to AES (reps and supervisors), I found out that as of November 2014, they have changed their policy to remove late payments when a back dated forbearance or deferment was granted and covers the dates of the late payments. However, anyone who had late payments prior to November 2014 would not benefit from the new policy. I was LIVID because my late payments were from early 2014. I tried to dispute by opening a case with Omnibus, but they were no help! Finally, I decided to file a dispute through CFPB website explaining that AES has changed their policy, but refuse to apply it for customers whose late payments were before November 2014. AES responded agreeing to remove the late payments from ALL 3 Credit Reporting Agencies. I have since checked my credit reports and the late payments were removed! Hope this helps anyone else in the same scenario.
Nice job! Thanks for the heads up about that policy, I had no clue.. could be HUGE news for many people here with AES lates. I have some lates from '14 and '15 that I am pretty sure I have a backdated forbearance on.. if not I will try to get one granted tomorrow 
I sent a letter to AES just now requesting a list of dates my account was in a forbearance/deferment status so I will follow up if I have similar results.
You can log into your account online, go to the message center, and view the letters they sent you. If there was a forbearance or deferment, the letter would be there and the second or third page of each document would list the dates you were covered under the forb/defer.