Hi, Clémentine 

Thanks for reaching out to us.

Please add this custom CSS to the booking page, and it should hide the price from the New Form :

.am-select-service-price{
    display: none !important;
}

Custom code needs to be applied to the page where the booking form is. Depending on what you're using (Gutenberg blocks, or some page builder), adding the CSS or JS can be done in a few different ways. 

If you need help with adding custom CSS to the page, please take a look at this article.

I am  not sure if it will work for you, for my site it worked

Please let me know if it works on your end. Thank you

And for the last step, this CSS :

.amelia-v2-booking #amelia-container .am-fs__congrats-info-customer>div:nth-child(6) {
    
    display: none !important;
}

So try to add them both, and let me know how it goes Thank you