Query credit balance with *101# / Guthaben mit *101# abfragen

[MonCon]

I just tried and had the same behaviour on my Manjaro OS, and when I tried to be clever and created the string in 'text editor' and copy-pasted it into the dial pad entry box it crashed the dialer app.
I can input *101# into UBPorts OS though, not that that helps if you prefer Manjaro.
Sorry, that doesn't really help.