Uh, there isn't an "iOS Store". I believe you mean the App Store. ;-)
I don't know anything about Linked In subscriptions. If you think you need to cancel a subscription, read this document: How to cancel a subscription from Apple - Apple Support
Subscriptions will continue until the expiration date. Canceling them just tells them not to renew after that date. To have it end before that date you need to contact Apple and explain you need it to end immediately.
Click here --> https://support.apple.com/choose-country-region/media-services Select your country, then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
or:
Contact Apple for support and service --> "See a list of Apple phone numbers around the world." Click here --> https://support.apple.com/HT201232