They nerfed the $100 of AWS credits for Alexa developers with zero notice this month, which caused me to incur overages this and last month.
I've gotten last month's bill waived, but still received a passive-aggressive email with bad English by a Territory Account Sales person from my region about how my account could be suspended, if I didn't reply to the email within the day. I'm not sure I would trust said person to handle my accounts, even if I was on a corporate budget.
I'm still in the process of moving most of my workload away from AWS.
Unless they call you, refuse to negotiate and still send it to collections as it is (at least in their mind) a legitimate charge.
All these stories of providers giving "good will" credit for these massive charges really concerns me when you look at how other parts of these companies ignore their customers or only reply with scripted responses.