Well, they had a point with their reply. You did not make a duplicate payment (for the same order), but you placed a duplicate order (due to misleading information on the AliExpress site).
It's the closest I could find after lots of chatting with the chatbot for about an hour. Support should not be a slot machine.
I'm not offended by them saying no. I'm offended by them saying no and then also:
(1) Not helping me find the right way of solving the problem.
(2) Telling me this is a brick wall, go away, we won't reply or discuss this further.
(3) Telling me to take an inappropriate action (show my bank this email & evidence if I still have a problem) that would probably get me banned from their platform. Did they seriously think this through?
In retrospect it's easy to say "that's not a duplicate transaction" because they provided strict definitions after the fact. That's about as rude as going to someone at a front desk, explaining your problem, then being told to leave the moment you use slightly the wrong words according to their internal corporate dictionary.
"But I did pay twice" "That's not a duplicate payment, go away, we will not reply, we will not allow you to engage further unless you come back another day". You're now standing outside again, in the rain, clutching your receipts and planning what words you will use before entering their building again.
I avoid those online chats (bot or human agent) if I possibly can, for the very reasons and frustrations which you described. Googling for "Aliexpress cancel order" brings up a reasonably helpful Aliexpress support page as the first hit:
Solving this myself feels very unwise. If it was caused by a website/db sync bug: what other problems might occur when I cancel? Perhaps it will cancel my original orders but not both transactions. I might even inadvertently do things that are against the site's rules. I've dug myself into holes before trying to solve problems on purchase/payment sites from my end, I've learned that you have to immediately get on the phone with the company. Often they'll tell you it's a transient bug until payments are cleared or something similar, ie "don't touch anything".
I have now cancelled two of them, as per support's advice, and the other two I'll have to dispute at a later date when that feature gets unlocked on the orders, as per support's advice. If things go skewiff I'm going to have to waste more hours, but at least I have some chat transcripts as evidence that I'm doing "the right thing" at all times.
I had a similar issue, somehow I ended up paying twice for an item, and they refunded me within a week. Didn't even had to open a dispute.
Good to hear
I presume that you didn't have duplicate orders too, however? Maybe they automatically were able to fix that.
"Dispute" is an Aliexpress-internal term that (I think) means "dispute with seller" not "dispute with Aliexpress", but I may be wrong.