Another way to call a POST method with AFNetworking 3.0 is:
AFHTTPSessionManager *manager = [[AFHTTPSessionManager alloc]initWithSessionConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
manager.requestSerializer = [AFJSONRequestSerializer serializer];
[manager.requestSerializer setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
[manager POST:url parameters:parametersDictionary progress:nil success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
NSLog(@"success!");
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
NSLog(@"error: %@", error);
}];
Hope it helps!