Due to how Sezzle checkouts work, there isn't a way for an order to be placed without access to either your phone itself or your Sezzle account. Because of that, it's very unlikely an order on your Sezzle account was not placed by you.
However, it's not uncommon for merchants to ask that a different name be listed on their Sezzle account than what their website operates under. This can cause orders to appear on your Sezzle account that do not appear to be from a familiar merchant.
If you see an order on your account that you don't recognize, we recommend checking your email for order confirmation emails from around the same date - it's very likely you were sent an email from the merchant for the same euro amount matching a merchant's name you're familiar with. Additionally, you may want to do a quick Google search to see if you're able to pull up their website.
Finally, some merchants will split up their orders when it comes time to ship. For example, if you had a 100 € order and the merchant shipped 25 € of merchandise, they might actually process a new order of 25 € and issue a refund of 25 € to the original 100 € order. This can suddenly make your account look like you have more orders with a merchant than you actually placed, especially since the refunds might not appear immediately. If that's the case, we recommend you reach out to the merchant directly and have them look up all orders under your information so they can clarify the status of your order and any refunds they may be issuing.