"Automated call"

My elderly parents have been receiving repeated numbers from a call which asks them to confirm their identity by pressing a number on the keypad. They were afraid to answer the call as they didn't know who it was from. The repeated calls were worrying them. I researched the number calling, which fortunately was not withheld. It appears to be an automated NHS service for reminders for inoculations and other appointments. However, I am happy that they refused to answer as they have recently had an unpleasent incident of identity theft resulting in their bank account being emptied. If this is a genuine number, I feel that it should identify that it is an NHS call before anything else.