You can not be billed £15 for placing a phone call.
There are premium rate numbers that cost up to £1.50 a minute, but the scam email you have received is another form of "Chain" email.
What is ransomware and how do I protect my PC from WannaCry?
What I learned from my mentor, Oscar-winning VFX supervisor Phil Tippett
Siri vs Google Assistant
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.