My dad is visiting from Europe - using a Lumia 930 with a Vodafone Italy SIM (Roaming is off)

Since about yesterday morning he's been unable to make ANY calls (including free VFIT service numbers) - he gets a recorded message from Spark saying that this call cannot be made and to ring *123

The main thing to mention is that during the first 2 days, the screen showed VFNZ, since yesterday it is showing Spark.

Any ideas?