Something I haven't thought about as a alternative may be mobilkom.li! They offer great roaming packages on top of their monthly subscriptions. Have a look here:
http://fl1.li/de/tarife/telefonieren...1-talk-roaming
You will get a Liechtenstein Number, but as I am aware of it is also possible (since mobilkom.li is a spin off of Mobilkom Austria) to get a Austria 0664 Number (additional).
Mobilkom is a partner of Vodafone, so you will always roam on Vodafone networks where available...
BK
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