Just in case, since manufacturers' sizing is often based on the phase of the moon and the colour of your eyes, do not trust that the XL is not a Medium.
Unless there are measurements in the listing, and the seller's feedback has no negatives or neutrals for poor sizing, it may be best to receive and try on the garment before making a decision.
If it is too late to stop shipment (and most sellers try to get sold items into the mail within 48 hours or lless) you can try on the shaper* and if it doesn't fit, it can be returned as unwanted. This is not a Not As Described dispute and you will have to pay return shipping with Confirmation of Delivery.
* It's not necessary to mention that you should wear undergarments and leave any tags intact, of course.
