We regret to hear that you want to cancel your XING subscription.
As the subscription was purchased via Apple iTunes, the cancellation must also be done via Apple iTunes.
Here is how to proceed with the cancellation of your XING subscription:
1. Go to "settings" in your iPhone.
2. Tap on your name at the top ("Apple ID, iCloud, Media & Purchases").
3. Tap on "Subscriptions".
4. Select the XING subscription and deactivate the automatic renewal.
If you have issues with the cancellation process, please contact the iTunes support directly.