I was listening to internet radio on the phone last night when a message came up asking if I was using wi-fi and would I allow a free phone call to Three so they could check up on it.
Was this message genuine and if so what is the purpose in asking if it was wi-fi connection?

never seen that. I listen to internet radio on my handset and never get messages.

you have been a bit vague, as to what phone you've got, what app you were using, and how the message appeared though.

Too vague, what number did it come from, what app were you using etc...

I use tunein radio and never had a problem. Im on the oneplan which includes tethering wheras other unlimited plans do not. What plan are you on? They may have seen high data use and thought you were tethering.

I use Tunein radio and have Internet Talker 300 plan with 500mb data but have updated to all you can eat data a couple of months ago. On the day concerned I used 90.13 Mb

There was no number came up it was a box that appeared asking for permission to phone Three which I presume it did automatically. The app concerned was Tunein Radio.

Methinks possibly as part of the ageement you are expected to use wifi at home. Bizarre considering some would not have broadband at home. Tunein must be a monitored item then?

I've just noticed that tunein radio is now putting adverts on the screen.