Vertex AI billing - unexpected high amount charged

[lennert311]

Hi

Recently I tried the Vertex AI tool within Google Cloud as a part of an interview where you had to present a workshop. 

I made something within the starting budget and never gave permission to start charging or deducting from my credit card.

Yesterday I received a bill of $2800, apparently it has been running in the background (which I never knew) and it charged me several $100's a day. 

I can't seem to get in contact with Google Cloud, the only service they're offering is a billing support page that tells me to shut down billing. 

I'm looking for a way to get a refund, since it's clearly a mistake that this has been running in the background without me knowing and since I didn't know they would charge me for it (since I was convinced it was within the 90 days and $300 free trial). 

Thanks in advance for your help!