[5e92cb50239222b]

It is impossible to spend any real money (as opposed to their $300 credit) without switching to a paid account, which is a multi-step process that you can't perform accidentally.

After the 30 day trial expires your account is switched to the "always free" mode. It does not allow creating any paid resources which are not marked as "always free".

[yonixw]

I was curios and read about it, and you are correct. But just like I said, there are many pitfalls. for example - I assumed you can change your paid plan freely but:

"...After I upgrade my account, can I downgrade?

There is no option to downgrade your account"

https://www.oracle.com/cloud/free/faq.html