Which things i can put in service in angular Js

I have read many articles but still could not find how to put stuff in services.

Currently this is my Service

angular
  .module('users')
  .factory('objectiveService', objectiveService);

objectiveService.$inject = ['$http', 'Restangular'];

function objectiveService($http, Restangular) {
  return {
    getObjectives: getObjectives,
    getSingleObjective: getSingleObjective
  };

  function getObjectives(pid) {
    var pr = Restangular
      .all('api')
      .all('users')
      .one('subjects', pid)
      .all('objectives');

    return pr;
  }

  function getSingleObjective(oid) {
    var pr = Restangular
      .all('api')
      .all('users')
      .one('objectives', oid);

    return pr

  }
}

This is the controller:

var _vm = this;
this.objPromise = objectiveService.getObjectives(44);

function getData() {
  var promise = _vm.objPromise;

  promise
    .getList(filters)
    .then(function(result) {
      $scope.gridData = result;
    });
}

function remove(id) {
  if (confirm('Are you sure you want to delete this!')) {
    objectiveService.getSingleObjective(id).remove().then(function() {
      $scope.getData();
    });

  }
}

// initial call   
$scope.getData();

In this code i basically see no use to define service because I still has to use then() in the controller to assign data to Grid.

Also I can't use then() in service because there I don't have $scope to update the data.

People say to do all stuff in service but I am not able to figure out how.

Ideally I want to put all functions like remove(object_id) in service

IS it possible that I can just do objectiveService.remove(id) in controller.

But then I have to call $scope.getData() after deleting which I can't do in service