I have this problem too - only, it happens a LOT. I've had people use my Gmail address but without the "." to sign up (or try to) for Playstation accounts, Apple accounts, Paypal, Skype, Bank accounts, plus it's pretty common that I receive wills and other sensitive legal documents, property deals, you name it. The legal docs etc are likely due to other people mishearing/mistyping someone's email which I can understand, but I'm constantly baffled by how often people must type in their OWN email address incorrectly for important situations too.
Often I can just ignore the signup confirmation emails and it doesn't go any further, but it's surprising how often there is no confirmation link sent out and the account gets opened without verification of the email address. At that point, it can be incredibly difficult to get the problem rectified. Most companies don't seem to have any procedure in place to deal with this situation - Many online companies only have an easy way to contact them if you are one of their customers, so I often have to resort to resetting that user's password to get into their account and use the company's contact form to try and get things straightened out from there. Sometimes even that isn't possible, e.g. because 2FA prevents me from resetting the password, so about the best I can do is unsubscribe from their marketing emails and leave the account active.