In fact, all payments made in iOS are handled by Apple. All subscriptions purchased in iTunes/Apple Apps Store are linked to your Apple ID (and not to the Ultimate Guitar account).
In order to cancel (unsubscribe) your Tone Wizard subscription in Tonebridge on your iPhone, please follow these steps:
- Open your device's Settings and tap on "iTunes & App Store".
- Tap on your Apple ID, then tap on "View Apple ID".
- In "Subscriptions" section tap on "Manage".
- Choose an app subscription you want to cancel.
- Tap on the toggle to switch it Off.