Can a website on safari give you a virus?
Do not contact the number it is a scam.

This is my advice from several sites including an Apple support document Note the document covers both OS X and iPhone/iPad/iPod Touch.

On iOS this is just a javascript pop up which just affects the page you are on and is just a message. To get rid of it close the browser,  iOS 9 might then prompt you with a Block Alerts button, if so tap the button to stop showing alerts from that webpage.

If you can't close the page then force quit the browser and don't go back to that page.

The writer of the script wants you to ring and the discussion will include asking you for money, it is a scam.