After many years of using complicated radio systems of varying degrees of complication and reliability, we have finally settled on a foolproof method for communicating callouts from top camp to base camp: mobile phones. Cheap Austrian pay-as-you-go mobiles have sufficiently good reception on the plateau for sending SMS messages, and even occasionally for conversation.
We are using the "B-Free" mobile scheme. (In 2011 we tried using another proveder which picked up the T-Mobile network, however the reception was not as good as B-Free. B-Free has an annual renewal of the SIM which gets you the phone number and connection (plus some credit). More credit comes in the form of a card with a scratch-off secret number.
This has to be done in less than 13 months otherwise it costs a great deal extra (equivalent to starting from scratch). The phone cannot be used in the last month, but renewal is much cheaper than starting from scratch.
If you need to buy more credits for a phone either:
You should be given a aufladecode, (this may require scratching off a panel at lower right back of card)