Thanks for bringing this to our attention and a warm welcome to the community.
The engineers when they test the line should do so to a free-phone number not a chargeable one. The engineer may ring a mobile if they believe the number is covered as part of the package so my apologies if this was not the case for you and our tech got this one wrong.
I'm glad to hear this call was credited and we will always make sure that any issues or mistakes are corrected as expeditiously as we can for our customers.
I hope the rest of your journey with us so far has been a better one.
Take care and don't be a stranger round the forums