Received a call, to my landline, from 07926615238 saying that they were BT and that my connection had been compromised and was being used by another IP address. Then received a text, to my mobile, with a two step authentication passcode on a number that BT have used in the past to arrange appointments etc (64364). Is this genuine? If not how did they get my mobile and landline and send messages from a BT number? When I told the caller that I had difficulty understanding her, she hung up.
My instinct tells me 99.9% scam
The phone number that they are using has no doubt been "spoofed" to make it appear to be a genuine BT call.
As regards how they got your number, that could be obtained in any number of different ways.... you entered your phone number somewhere on line and this has been compromise..... they have obtained it from a crooked employee of a genuine business ...... etc etc.
@hclements They don't have your mobile number. They try and access your BT account by going through the Forgot Password route. BT then send you the text, so it's genuine. The scammers then ask you to read it back to them, to prove it's you. They can then access your account and change the password. They usually work in pairs, one keeps you talking on the phone while the other does the dirty work. If you didn't give them the code you're OK.