I am very new to Magento development and need to be pointed to the right direction to solve my issue.
Although I have found a few questions that tackle similar topics (Hide particular payment method if subtotal is zero and http://www.onlinecode.org/magento-disable-payment-method-programmatically/), I have not been able to use any of it, sometimes because I lack the detailed knowledge of Magento develeopment and sometimes references are not explained properly. Maybe the idea is too simple or too uncommon:
We are allowing customers to apply coupon codes on their cart. in some cases the coupon amount is greater than cart's grand total:
Sub Total: USD 100.00
Coupon Code: -USD 110.00
Grand Total: USD 0.00
When checking out (One Page) - obviously - there must not be a step called "Payment Method" because cart value is 0. Currently we have one payment activated for our customers (Credit Card) and "Zero Subtotal Checkout" is disabled, simply because we do not want to confuse our customers (if we show the payment step, they might think "My order is supposed to be free, no?")
I thought, if we could only have a condition inside our code to skip this one step only, when value of cart is 0.
Many many thanks