"Unsupported" doesn't mean "except for you"

cust: We're having problems with YourBigApp on Citrix.
me: I'm not surprised. Citrix is unsupported.

cust: Yeah, we know it's not supported. But anyway, we set up YourBigApp on Citrix...
me: But we don't support Citrix. It won't work.
cust: Fine. Let me finish. So we set it up on Citrix and it mostly works, but there's $Problem1 and $Problem2
me: I know. Those are the reasons Citrix is unsupported.
cust: But we need a solution to $Problem1 and $Problem2.
me: Talk to Citrix.
cust: But Citrix works.
It's YourBigApp that doesn't.
me: Does OurBigApp work in a non-Citrix environment?
cust: Yeah, but it doesn't work on Citrix.
me: Exactly. Our app works.
cust: But not on Citrix
me: So talk to Citrix.
cust: But Citrix works! And Citrix says all apps work on Citrix.
me: So ask Citrix why OurBigApp doesn't work.
cust: We did. They said to talk to you.
me: Citrix is unsupported.
cust: But you HAVE to support it. We did all our development based on using it.
me: Did you search through the knowledge base on "Citrix AND OurBigApp"?
cust: Umm... yeah?
me: No. Because if you had you would have seen $doc1 and $doc2 and PublicTickets 1, 2 and 3, all of which I wrote which explain why Citrix won't work. Our search was tweaked to ensure these documents always come up as the most relevant whenever a search includes "Citrix".
cust: But, but, but... but we NEED it to work on Citrix.
me: So tell Citrix.
cust: But it's YourBigApp
me: Yes, it's OurBigApp which works fine without Citrix, that we explain won't work on Citrix, that we explain why it won't work on Citrix (because they lied to us during development), and that Citrix will have to support if they claim it'll work on their system.
cust: But, but, but, but ...
me: Ticket closed. Root cause: Customer. Reason Code: 12-Unsupported Environment. HAND.

You know this should be a 17.