At one point I tried using AWS trial for an app, didn't work out, cancelled the account (or so I thought) only to find 2 years later some charges to my bank of $2k and when I spoke to AWS support, there was another $4k accruing for this billing period. Took ages to sort out, while they eventually did refund the amount, I was still out of pocket exchange fees (X2) the exchange rate also meant I was out more money. In total I think having a compromised yet closed AWS free trial cost me $350 over a 6week period some 2 years after closing it.