Payment Method

https://www.mapsmadeeasy.com/subscribe_paypal

You need to email us at mapping@dronesmadeeasy.com to tell us after you have made this payment since this is added manually. 

I tried the payment method with Google Pay, but why do I have to enter my credit card number? I don't have credit card and I want a monthly subscription.

I don't think it says anywhere that Google Pay is supported. If it is shown as a payment method and asks for a credit card number that might just be how Stripe (the credit card processor) does it.