You can go to this link to view, change or cancel your subscription purchased through the App Store: https://support.apple.com/en-us/HT202039, or follow the instructions below.
First, go to "Settings" on your iPhone, iPad or iPod.
Tap "iTunes & App Store".
Tap your Apple ID.
Tap "View Apple ID". You may need to sign in.
Under "Subscriptions," tap "Manage".
If a subscription doesn't appear in iTunes, but you're still being billed, make sure you're connected with the correct Apple ID. If this is the case, you may have subscribed directly with the provider and not with iTunes. You'll need to contact the provider in order to cancel your subscription.
Click on your FizzUp subscription to cancel.
Use the options to manage your subscription. You can modify the subscription period or deactivate the automatic renewal.
Deactivate the "Automatic Renewal" function to cancel the subscription. It will be canceled at the end of the current billing cycle.