Error 2: Failed to connect to device as it is pin locked.

When trying to run a Windows Phone application on a device for the first time, you might get the following error:
Error 2: Failed to connect to device as it is pin locked. 0 0

Solution: Register your phone for development with Microsoft.
Note: if you still get this error after registering the device, you might need to restart Zune & Visual Studio.

No invoice for Windows Phone developer registration fee

I registered to Microsoft's App Hub (Windows Phone developer account), paid the registration fee (~100$), but I didn't get an invoice. Checking online only made it clearer that Microsoft does not send an invoice for App Hub registration fee since more people had the same problem.

I opened a ticket at App Hub support here: https://windowsphone.create.msdn.com/support

I've waited for 4 days and got no answer, than:

(1) I asked a friend from Microsoft what to do. He sent me to Microsoft regional support.
(2) Calling the support they redirected me to MSDN support (since the registration is on create.msdn.com).
(3) MSDN Support told me to send an e-mail to apphub@microsoft.com
(4) The answer from apphub@microsoft.com was to open a ticket at Hub App support..... CRAP.

I still don't have an invoice, but I do have second thoughts about developing for Windows Phone.
Way to go Microsoft.