Why huge AWS Personalize bills for unused service?

Several months ago I wanted to test out AWS Personalize and uploaded a 35MB .csv file with some data, abandoned it and certainly didn't "use" the service in any way. Nevertheless AWS has been billing me around 1000EUR a month, for "2,157.000 Recommender Hours - $0.375 per recommender hour for first 100k users"

Needless to say I'm horrified at having been billed such a huge amount over 5000 EUR for a service I wasn't using (I only discovered it this late because my payment method is connected to a bank account that I thought was dormant with no reason for me to monitor it ... lesson learned)

The docs say: "With Amazon Personalize, you pay only for what you use. The costs of Amazon Personalize depend on data processing, training, and number of recommendation requests."

How can I find out what exactly I've been billed for? Is it possible that someone abused my account in any way? The 2175 hours on the last invoice corresponds to 90 days, so I guess 3 recommenders were running full time? Why would this be the case if this service is (afaik) not being used or accessed in any way?

Is there any way I can dispute or reclaim these charges?

Thanks