Error 'please enter service codes directly from the phone's keypad' "GSM "

Question

How to use PhoneCallTask to dial a Service Number with # and ***** in it

I'm using Nokia Lumia 520 Windows 8 after the confirmation the error message appears

                PhoneCallTask call = new PhoneCallTask();
                call.PhoneNumber = "*100#";
                call.DisplayName = "Fund";
                call.Show();

this number is to check my phone fund

Answer 1

No, that is not possible. The only way to start a call is using PhoneCallTask but that doesn't support service codes as you already found out.

Note* This functionality is only available to mobile operator apps.

Answer 2

When you "dial" a number like that it is not a normal phone number and it is not to be handled by the "make phone call" part of the phone, but rather the part that handles USSD (as you have correctly tagged this question). Thus without knowing the API you are using, you should instead look for something like PhoneUSSDTask to use instead of PhoneCallTask.