Some healers are literally Black Magic healers, and don’t tell you, but you can tell them because they use spells, and other summoning devices to get the healing done. If they advertise that they can bring a lover back, change your luck, or give bad luck to others, then that is certainly black magic, as the Light never does that since Free Will is the greatest gift God has given us.
Some black magic Astrologers/Healers see nothing wrong with black magic and say right in their websites that they use black magic. At least they are not hiding it from you.
Black magic always has a price, and by calling on the forces of Darkness, your Soul will be bound by whatever price the Demons and Entities want your Soul to pay. It is simply not worth the price, so don’t do it.
Read more on how the Dark Does Healing Too