I yesterday booked a holiday with travel company low cost holidays. Early this morning I received a mobile phone call from a withheld number asking me to verify my booking. The male caller asked me to confirm my name which he called out and give him the last four digits of my visa card/ account. I declined and said i would call him back. The call instead said he might ring me tomorrow. Due to early call I am unsure if the call was from the low cost holiday company or the booked hotel. My query is it safe to give out the last four digits of your visa card to callers like this?