Change banner image on mobile

Add to Design > Custom CSS

@media screen and (max-width:640px) {
section#details-top {
    background-image: url(https://content.invisioncic.com/p289038/monthly_2022_08/contact-mobile-1.thumb.png.f26621d0f1fef41ff98d7069f212f0af.png);
    background-size: cover;
    background-repeat: no-repeat;
    background-position: center center;
}
}