some one trying to tell me there had been suspicious acitivity on my Mastercard or visa Card and wanting my details!

A person called me from 00114 9973964207. Said he was from some security organisation and his name was Rex Rodricks. Told me he had detected two transactions on my credit card from the UK. Asked me to tell him which bank am I with. I hung up at that point and a few seconds later I had a call from (07) 4787 9803 which I didn't answer. No message was left.