Registration of phone number not possible for iMessage & Facetime

UPDATE: as of now (Jun 21, 9:00 am CET), phone# activation works again for both iMessage & Facetime. Didn't even have to re-enable any settings.

Just to jot this down, for Apple support or anybody else twisting their heads on the problem:

Currently (at least since 2 days ago, June 18, 2013) there seems to be a global issue with registering an iPhone's phone number for use in iMessage and Facetime: both screens remain in status "waiting for activation..." (German: "Auf Aktivierung warten...").
But: iMessage & Facetime both work fine with the Apple-ID.

Many similar complaints currently in the Apple Support Communities confirm the issue.
(Hint: this is on the latest and greatest iPhone 5 16 GB & iOS 6.1.4)


So...what gives?!?

Here's my chronology (all Pics in German, sorry):

Switching on iMessage & Facetime including Apple-ID usage shows the information expected:

But both status screens remain in "waiting for activation..." (German: "Auf Aktivierung warten...").

Also strange: since I switched SIM cards some days ago, my old phone number is still shown in the status screens, even though the phone itself works fine with the new number (both calls and SMS/text messages)!

Story gets even more funny: after yet another registration attempt on my side, I keep receiving text messages from the UK Apple Activation numer +44 7786 205 094. Not only 1, but at the time of this writing already 16 :)

Hint: the iPhone sends a silent SMS/text message to the above number on every activation try of iMessage and Facetime. This is not unusal. But receiving back not only one but many text messages is.

And by looking at the content of the message (hey, I'm a tech guy after all), it seems clear that it is a reply to an activation request:

And just for the record:

• yeah, I know of the Support Documents on how to associate your phone number with your Apple ID. Tried that manyfold: nada.
• yeah, I know of the Support Document on how to troubleshoot iMessage & Facetime, including the part on problems with activating the phone number. I tried that, including the suggested patient 24-hour-wait for activation. Guess what: nada.
• yeah, I called T-Mobile. All settings on my account are correct. I can receive and send SMS/text message, I can make calls. The iPhone really works fine - except iMessage and Facetime via the phone number.
• yeah, I called Apple Support. Yesterday, June 19. And they confirmed that there currently seems to be an issue with activating phone numbers for iMessage and Facetime. Yet the status support pages are all green - were yesterday, still are. Go figure.