code: public void singleStepTransfer(
              String connId,
              String destination,
              KeyValueCollection userData
      ) throws WorkspaceApiException {
          this.singleStepTransfer(connId, destination, null, userData, null, null);
      }
docs: Perform a single-step transfer to the specified destination.
  @param connId The connection ID of the call to transfer.
  @param destination The number where the call should be transferred.
  @param userData Key/value data to include with the call. (optional)