We don't want to use payment getways like 'Paypal' or 'Authorize.NET' Is there a way or option I can select so I can just collect the credit card numbers and process them in house?
Easiest way is to create your own custom payment gateway. I say "gateway" loosely.
https://docs.kentico.com/k10/e-commerce-features/customizing-and-developing-your-store/payment-related-customizing/creating-a-custom-payment-gateway
So the documentation shows how to process the payment using an external gateway. In your case, you'd just use the public override void ProcessPayment() method to store your data to a database for further internal processing (even though it will violate PCI compliance).
public override void ProcessPayment()
We're going to make them use the gateway, since violating PCI isn't an option.
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