Hello again,
On 2lounge.ch "Peter" reports that he made a phone call to the bankruptcy-administrator of United-Mobile. He told him, that Mobilkom of Liechtenstein bought the UM-Platform for themselves. So you can expect, the UM423 platform will return soon.
From the sudden switch off of +423 663 (for outgoing calls) to now its round about 6 months. Reminds me on the Globalsim-SIM-Card connected to Callkey @ isle of man...
Stay tuned and store your SIM card in a safe place.