当我在angularjs中调用http.post时如何修复$ interpolate：interr错误

Question

当我使用$ http.post调用web服务时，我正在使用AngularJS并面临$ interpolate：interr错误。

这是我的来源：

myportletServices.factory('Usage', ['$http', '$sce', 'Settings', 'Alert', function($http, $sce, Settings, Alert){
    this.query = function(callback){
          var url = $sce.getTrustedResourceUrl(Settings.webServiceUrl + '/usage?userid=' + Settings.screenName);
          var http = $http.post(url); //--> Error occurs
          http.success(function(data, status, headers, config) {
              if (data.ok==true) {
                 if (callback)
                     callback(data.result)
              } else {
                  Alert.add('Alert', data.message);
              }
          });   

          http.error(function(data, status, headers, config) {
              Alert.add('Error', data);
          });
    };

    return this;
 }]);

从服务器返回：

{
   "ok": true,
   "message": "",
   "result":
   [
       {
           "phoneid": xxxxxx,
           "phonenumber": xxxxxxxx,
           "planid": xx,
           "planname": "$29 Plan",
           "cap":
           [
               {
                   "stdcap": 165,
                   "datacap": 100,
                   "smscap": 0
               }
           ],
           "usage":
           [
               {
                   "stdusage": 97.99,
                   "datausage": 56.044,
                   "smsusage": 0
               }
           ]
       },
       {
           "phoneid": xxxxx,
           "phonenumber": xxxxx,
           "planid": xx,
           "planname": "Essentials $45 Plan",
           "cap":
           [
               {
                   "stdcap": 650,
                   "datacap": 1000,
                   "smscap": 6000
               }
           ],
           "usage":
           [
               {
                   "stdusage": 116.51,
                   "datausage": 253.339,
                   "smsusage": 63
               }
           ]
       },
       {
           "phoneid": xxxxx,
           "phonenumber": xxxxxxx,
           "planid": 80,
           "planname": "Medium $25 Pack",
           "cap":
           [
               {
                   "stdcap": 500,
                   "datacap": 1500,
                   "smscap": 6000
               }
           ],
           "usage":
           [
               {
                   "stdusage": 90.05,
                   "datausage": 115.237,
                   "smsusage": 108
               }
           ]
       }
   ]
}

错误讯息：

Error: [$interpolate:interr] http://errors.angularjs.org/1.3.0-beta.2/$interpolate/interr?p0=%7B%7Busage…usage.planname%7D%7D&p1=TypeError%3A%20undefined%20is%20not%20a%20function
    at Error (native)

我找到的错误与使用错误的表达式格式有关但我的情况发生在我从webservice获得结果时。是否会发生因为返回数据有特殊字符，如美元符号？

请解释错误并提供一些帮助以解决问题。 谢谢，您的帮助将不胜感激。