Change waitlist default text on product site from product to service

Hi, 

Some of my services are sold out and I have activated the waitlist sign up on my website. I would now like to change the text ""Get notified by email when this product is in stock" that appears above the waitlist sign up field on the product pages when they are sold out. Can anyone help me with this? Big thanks in advance. 

You can use this code to Website Tools > Custom CSS

span.product-restock-cta {
    visibility: hidden;
}
span.product-restock-cta:before {
    visibility: visible;
    content: "email me when stock is available";
}