SCAM ... trying to pretend they are from Visa/Mastercard (which are two different companies!) ... tell you that your account has been accessed from overseas and they need you to install new software on your phone (which no doubt is malware of some description). Humoured him for a while and as soon as I said that this is clearly a scam he hung up. Delayed connection when they called (like most scammers) and noisy background (must have a lot of people working the phones!).