Apple's streaming service, Apple Music, was launched with three months of free access to the service, which usually costs $9.99/£9.99 a month. Now that those three months are up you could find your subscription automatically renewing, meaning you'll be paying for the service.
To make sure you don't get charged after the free period ends on September 30, open up Apple Music and tap on the account logo on the top left-hand corner of the app.
Next tap on View Apple ID and tap on that to sign in and then select Apple Music Membership.
This will bring up a list of options and under where it says "renewal options" tap on the toggle next to "Automatic Renewal" to turn it off.
Now you can continue using Apple Music for free until your trial ends, but you won't get automatically charged.