Orange promised me after this free trial of something expired, I would not be charged. They did charge me and I was annoyed enough that I cancelled the contract. I have never been with Orange/EE since, and never will. I think this was about 10 years ago when I was more stupid with this sort of thing, but still...he outright lied to me! And yes, I know they all lie now...and yes, I know the internet gives you far better deals...
And yeh, I'm weary of anything attached to something I buy that has a free trial. I make sure to get rid of it. I'm weary of signing up to any contract. Monthly renewal contracts are a great idea.
I would certainly keep on at them about cancelling that contract at the very least, if that's what you wish to do. Surely it would be invalidated as she is underage.
Maybe the Citizens Advice Bureau could help you, if you're in the UK.
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I've left WP.