How to resolve payment issues of app subscription on the App Store

If the in-app purchase is not shown for the app, then review this Support Article:

If you can't find or use your in-app purchases - Apple Support

What is the name of the app and what did the developer say about the in-app purchases not registering? The developer is able to give you Promo Codes for in-app purchases that you had trouble with.

Request and manage promo codes - Offer promo codes - App Store Connect - Help - Apple Developer

When disputing a charge through the bank, your card will be cancelled and will not be usable in any location. The bank will issue you a new card. That is not Apple threatening any action, that is simply what happens when bank disputes are made. You will also have to notify any other company if you have subscriptions or auto payments using that card as those payments will be declined after a charge on that card is disputed.

There is a big difference between disputing a charge and closing an account. When a dispute is opened with the issuer of the card, the bank must credit the disputed amount and investigate the situation. The card issuer will allow each party to submit statements and any pertinent documents. The issuer will then make a decision that will be final, at least as far as the issuer is concerned. If the decision is in favor of the merchant, funds are returned by the issuer to the merchant and charge to the account holder is reinstated. If the decision is in favor of the account holder, the credit is made permanent. In either case the merchant is charged fees and disputes cost merchants a lot of money.

The only time your scenario plays out with canceling cards is in the case the account holder says the charges are fraudulent. A dispute does not close the account and the card can continue to be used at other merchants. It’s certainly within Apple’s rights to restrict use of a specific card or close Apple ID accounts and respective store accounts.

The terms and conditions of the credit will spell out how disputes are handled, timelines and what qualifies as a dispute. Cancelation of an account is not a part of a dispute unless the bank suspects abuses. Credit card billing is governed mostly by the Federal Fair Credit Billing Act.

https://consumer.ftc.gov/articles/using-credit-cards-and-disputing-charges