I got a 5$ charge on my account, I didn't buy anything or get a notification about it either. My wallet doesn't even reflect having the 5$
You want to take this up with customer service.
Go here. You can call the toll-free number or live-chat with them on the site.
I would also recommend contacting your bank/credit card provider.
And take your credit card info off your PSN account so nothing can be charged by anyone else using your console.
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Did you sign up for a free trial subscription to Music Unlimited, or something else, recently? The minimum amount of money that can be added to a PSN wallet is $5, so if you were a little short when a subscription was due for renewal, then your card may have been charged $5. All free trial subscriptions automatically renew as paid subscriptions unless you explicitly cancel them in the Services List.