Random Bill for £17.49 -

Just been billed £17.49 by Apple for some unknown App - nothing we have knowingly purchased...

Initially thought it was phishing but bank have confirmed payment has been authorised so it is genuine. the only thing I can think it is related to is that recently I added my wife's Apple Id to my Apple music (family account) - but this should be included in the £14.99 we already have

Anyone else experienced this or have any ideas what it might be - currently trying to get in touch with someone at apple to discuss but this doesn't seem straight forward