Error 406 $http POST

Hi I call a REST web service by mean of $http object.
In my android device I have a “406 not acceptable” error.

My POST $http call is:
$http({ method: 'POST', dataType: 'json', url: url, headers: { // 'Content-Type': 'application/x-www-form-urlencoded' 'Content-Type': 'application/json' }, data: { "AppId" : "11111111", "sCodTessera": "115594", "sEmail": "roberta@tiscali.it", "d_data_nascita": "21/01/1979", "id_sede": "3" }
This call should return a token id of the user for authentication.
Any suggestion ??