How to check if user exists in quickblox android api?

I am developing an Android application using quickblox, I am trying to check if usr exists using its phone number. Api does not return errors, but returns 0 for users found. I check the phone number on the quick access panel and is present ... what's the problem?

SOLVE: Having solved, the problem was "+", I encode as a URL and now works!

Here is an image about my panel with a phone for the user:

here is my code:

numero = "+393482222222";
              Log.v("Numero:", "-"+numero+"-");
              QBPagedRequestBuilder pagedRequestBuilder = new QBPagedRequestBuilder();
              pagedRequestBuilder.setPage(1);
              pagedRequestBuilder.setPerPage(5);

              ArrayList<String> usersphone = new ArrayList<String>();
              usersphone.add(numero);

                QBUsers.getUsersByPhoneNumbers(usersphone, pagedRequestBuilder, new QBCallbackImpl() {
                    @Override
                    public void onComplete(Result result) {
                        if (result.isSuccess()) {

                            QBUserPagedResult usersResult = (QBUserPagedResult) result;
                            ArrayList<QBUser> users = usersResult.getUsers();

                            Log.v("Found start chat", "start chat");

                            if (usersResult.getUsers().size() > 0) {

                                //  Apri la chat
                                //
                                appDelegate.sh.setOpponentId(usersResult.getUsers().get(0).getId());
                                appDelegate.sh.setOpponentNumber(numero);

                                avviaChat();
                            } else {

                                sendSMS();

                            }

                        } else {

                            Log.e("Errors",result.getErrors().toString());
                        }
                    }
                });