While automated phone calls can be annoying, I'd urge you to find out as soon you can why Santander have called you.
I got a 'robotic' phone message from Santander a few weeks ago, urging me to call their security people. I was suspicious that, by phoning back, I could be walking into a trap where I was required to give my card details (including my PIN) to someone purporting to be from Santander. So I was very cautious when I phoned back. However the only security details I was asked for (such as my address and date of birth) didn't relate to my card and it quickly became clear that the lady I was speaking to was genuinely from Santander. (For example, she had a full history of my transactions to hand, including cheques paid in as well as money drawn out).
The lady then explained that their system monitors cash machine withdrawals, checking for any suspicious activities. She asked me about three recent withdrawals made in East London. (I live in Suffolk). They totalled £800 and I knew nothing about them. (i.e. someone had stolen £800 from my account). After a few more questions, the lady said that she'd initiated a fraud investigation and that I should get my money back in about 10 days time. (It was exactly 10 days later when I got a letter from Santander, stating that the money had been refunded).
That number is genuine:
http://whocallsme.com...ber.aspx/008453512275
Santander are trying to help you keep your money secure. (You may well have already have had some stolen) I urge you to call them as soon as possible.
Chris