Hi,
if you are able to change the order by just running the FM in SM37, then it proves that you don't need a commit RFC.
I only now noticed that you didn't request any result parameters before creating the second rfc. In general it's a good idea to finish one rfc at a time and for now I strongly recommend to request some data back (even if you don't need it) before you create and send the next rfc.
The following is a script that I created with the RFC tool in SP03 and is working fine (well, it does not do anything, but it runs through and does not cause exceptions and the _RETURN1 object contains a sensible, functional error message).
var oRFC = session.createRFC("BAPI_ISUSMORDER_USERSTATUSSET");
oRFC.setParameter("INACTIVE", ""); // optional
oRFC.setParameter("NUMBER", "");
oRFC.setParameter("STATUS", {"INTERN":"","EXTERN":"","LANGU":"","LANGU_ISO":""});
oRFC.requestResults(["RETURN"]);
oRFC.send();
var _RETURN1 = oRFC.getResultObject("RETURN");
var oRFC2 = session.createRFC("BAPI_TRANSACTION_COMMIT");
oRFC2.requestResults(["RETURN"]);
oRFC2.send();
var _RETURN2 = oRFC2.getResultObject("RETURN");
Cheers,
Clemens
