The easiest option is to use the Upgrades screen where you originally subscribed:
Tap the map's More icon (on Mac, the Help menu), then "Upgrades"
Tap "Manage Subscription" to open the App Store's Subscription page.
Tap the inRoute subscription to manage/cancel. If there is no Cancel option, you have already cancelled. If there is no inRoute subscription, you have not subscribed recently.
Or, you can also manage subscriptions through your App Store account settings from your device or a computer. The link below from Apple has general instructions for any subscription on the App Store: https://support.apple.com/HT202039#subscriptions
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