With Vamos you can also use your mobile phone to call your colleagues using a short internal numbers, such as 381. However, there you need to keep the following restrictions in mind:
2-digit internal numbers can give problems because they can conflict with specific MMI codes
internal numbers starting with "00" will not work as this is seen as an international access code and is replaced by "+". For example, 0002 is replaced by +02.
4-digit internal numbers starting with "0" will not work as this replaced by "+". For example, 0444 is replaced by +444.
special reserved short numbers such as 112, 18xx, and 14xxx (x) cannot be used as internal numbers.