How to deactivte\close an Amazon AWS user (or at least the billing)?

Question

I had last semester a university course where I used AWS to do the homework, and later I deleted all instances, all volumes, everything. But it for some reason still counts hours (for now without charging me). But I would like to know how can I disable every possibility to get charged, just in case I forgot something (cannot find something) As stated I don't want to use their services anymore, so a brute-force account delete\disable is the best option for me.

Answer 1

Just contact AWS and request them to close it.

https://aws.amazon.com/support/