fix syntax

src/sipcentric/__init__.py

@@ -282,13 +282,13 @@ class Customer(APIObject):
             yield LinkedUser(self._api, data=c)
 
     def limits(self):
-        return Limits(self._api, self._api.get(Limits.makeUrl(parent=self))
+        return Limits(self._api, self._api.get(Limits.makeUrl(parent=self)))
 
     def callcharging(self):
-        return CallCharging(self._api, self._api.get(CallCharging.makeUrl(parent=self))
+        return CallCharging(self._api, self._api.get(CallCharging.makeUrl(parent=self)))
 
     def permissions(self):
-        return Permissions(self._api, self._api.get(Permissions.makeUrl(parent=self))
+        return Permissions(self._api, self._api.get(Permissions.makeUrl(parent=self)))
 
     def create(self, parent=None, **kwargs):
         if parent: