groovy.lang.MissingMethodException: No signature of method with String

Question

I'm new to Groovy and I run into this error that I don't really understand.

groovy.lang.MissingMethodException: No signature of method: getUsers() is applicable for argument types: (String, String, String, String, String, String) values: [ABC, DEF, GHI, JKL, ...]
Possible solutions: getUsers(java.lang.String, java.lang.String, java.lang.String, java.lang.String, java.lang.String, java.lang.String)

This error happens when I called this method within another function that has the same parameters:

public List<String> getResponse(String userId, String firstName, String lastName, String email, String address, String date) {
        try {
            def response = null;
            response = User.getUsers(userId, firstName, lastName, email, address, date)
        } 

Thank you so much for your help!