Bizarre goings on! Possible hacking?

Hi All

I’ve just had an email from a client who’s site I maintain. A customer has sent them a screen shot of their site and the telephone numbers they are seeing is not what’s on the site. This occurs both in the headers and contact page.

I have been through all pages looking for unknown scripts, I’ve search the code for the phone number in question and also wordfence hasn’t picked up on anything either. I’ve also asked a few people globally to check the site and they all see the correct phone numbers.

Has anyone ever heard of anything like this before? Could it be something locally on their customers computer maybe? They were using Safari, so I doubt it could be a virus, but you never know.

This one’s got me puzzled!

Thanks