Hi lusine144,
welcome to the Apple (user-to-user) Community!
Re: issue regarding my recent subscription to the Promova App's free trial version
A Free Trial needs to be cancelled at least 24 hours before it expires, in order to not be charged.
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Re: I’ve decided to discontinue.
What to do: If you want to cancel a subscription from Apple - Apple Support
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To check if Apple has charged you:
See: If you see 'apple.com/bill' on your billing statement - Apple Support
and
If money has been deducted (not pending) via Apple:
You can: Request a refund for apps or content that you bought from Apple - Apple Support
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Else:
You might want to check how in-app purchases work:
Buy additional app features with in-app purchases and subscriptions - Apple Support
Also:
The best source of help for a product not made by Apple (a third-party product) is the company or person who made it—its vendor or developer:
How to: Contact a third-party vendor - Apple Support
and
How to contact an app developer - Apple Support
All the best :-)