There is a much more easier way to get in touch with them (if they answer the phone). Searching the public Swiss phonebook gives you this result:
Firmeneintrag vCard WebStamp SBB Speichern Ändern
United Mobile AG
Schaanwald Kloten Branch
Obstgartenstrasse 27
8302 Kloten/ZH
+41 43 204 28 28.
After having contact with them last week on wednesday, they assured me to shift my balance from my ICQ Sim to a +44 UM SIM that will be posted to me. One day later they had the service outage of +44 platform as well. Tried to call them and got an answering service telling that all platforms are down at the moment and they will fix it as soon as possible. When calling later that day, the message were switched to "you are calling us out of our business hours".
I tried right now to call again and it says "all our lines are busy at the moment, please wait" and you get disconnected after about 3 minutes or so. There IS someone at the office, regardless if they went out of business or not.
By the way, I have ordered on of those SIM4travel replacement cards that are offered for free, and they did arrive within 3 working days within europe. Altough they are not really free! They state on the website AND the bill enclosed Free SIM and free postage, but charge 6.someting Pound for shipping 2 free SIMcard by registerred mail.
Greetings, BK
PS: Funny enough, I were on the local Swiss Post office on Friday and they still sold United-Mobile SIMcards. I've asked the clerk about any news updates and he told me, there has been an information about service problems of +423 on wednesday.

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Mobiles: iPhone 7+, iPhone 7, iPhone SE, Blackberry Priv, Honor 8, Lumia 950
Prepaid-SIM: 3 UK, Save Money Sim, Toggle Mobile UK, XX-Sim, Koko Mobile