I have the following problem, in fact there are 2 situations:
1st situation:
I need to remove the "buy" button when the product is not priced.
I'm doing a store with woocommerce where there are several products and I registered them as variable products, however some of them have no price registered (because we do not have the values of these). I included a button to redirect the customer to the contact area so we can negotiate the order. However, I need to remove the option to purchase this field when the product is set to zero.
2ndSituation
Whentheproducthasaregisteredvalueandhasnostock,itispresentedasfollows: 
I need it to appear with the same message as the 1st situation and also without the buy button.
Could someone give me a light?
Thank you!
Product Link:
Woocommerce version 3.2.5 Wordpress version 4.9.1