as far as i understand, your "payment-method" is not tied to a device or system, it uses the method, you registered your number for the first time.

for example, one who used the "one-time-pay-method" on iPhone when he registered first time does not change to the "yearly-pay-method", when he switches to android.

i used an old Symbian device when my screen was broken and used whatsapp on it whithout problems, this did not change my "payment-method"