See also: Anyone ever had to consume WSDLs from Elixir?.
Seems to boil down to working on the HTTP/XML level - unfortunately that means understanding XML and the relevant parts of SOAP (which are likely buried behind the majority of specifications not relevant to your case).
Well, SOAP isn't a "modern" specification, so it's only (somewhat) well supported by the technology stacks that were mainstream when the big vendors were pushing WS-Deathstar (Java, .NET) - so all that technology is already in place. However building a new set of SOAP tools for a younger language from scratch is an unforgiving and unrewarding task because of all the complexity buried in the WS-* specifications to support scenarios that are largely irrelevant for point-to-point data transfer but can come into play whenever your "SOAP-partner" starts to fiddle with their configuration because their tools allow them to.
SOAP: now that everything is said and done, we built RPC again