If you purchased through the XBox store, it's MS who took your payment and have the record of your transaction and you really need to talk to them. ZOS would only be the first point of contact if you'd bought through the ESO store.
It's unfortunate and I'm sure very frustrating that this happened, but a transaction made by mistake is not a theft. Regardless, this issue is not going to be fixed on the forum so I'd suggest trying to follow up via the links provided and/or by continuing to contact support for further information.
The ability to get a refund likely depends on the terms of the transaction and the policies of the actual party to the transaction (for example, Steam clearly labels ESO Plus as a non-refundable purchase). As others mentioned, if the purchase was made through a third party platform, they are the ones who actually took the payment and have the necessary information. If xbox/ms are unable to help either, it might be worth following up with zos support to see if there's anything they can offer to help make it right.
We have closed this thread due to the original issue has been resolved. I feel the need to clear up any misinformation that can be caused by the previous statement. We do not use AI Agents for customer support. Every support ticket is answered by a human.