In app subscription with credit card I'm using an app that allows the user to sign up for a subscription. Doing that in the app the user is asked to type in their credit card  information. 



Is that allowed for a Play Store app? In Play Store terms it's stated that:


  In general, the terms of Google Play allow you to sell in-app subscriptions only through the standard payment processor, Google payments.


I asked the app developer about this, but they replied with instructions for doing a subscription on iTunes (without having to type in credit card info).
It's not clear from your question or the app description exactly what a premium subscription gets you, so I don't know if this applies to you, but there's an exception to the rule you quote. Purchases of goods or content that isn't just accessible through the app don't have to go through the in-app purchase system or Google Pay.

Quoting Google's Developer Policy Center:


  
  Developers offering products within another category of app [other than games] downloaded on Google Play must use Google Play In-app Billing as the method of payment, except for the following cases:
  
  
  Payment is solely for physical products
  Payment is for digital content that may be consumed outside of the app itself (e.g. songs that can be played on other music players).
  
  


If the subscription this app offers is for videos or music, or it's also available through their website, they don't have to use Google Pay.