Since I have been here, I have taught three lessons during Sunday morning church service. Each lesson was about serving God faithfully because he is the greatest King and greatest power. The Kaonde live in constant fear of their ancestors, evil spirits, and witchcraft. I have tried to teach that although any of those might kill us, only God can judge us and send us to hell (Matthew 10:28). God is more powerful than any other power and even Satan can only act with God's permission (Job 1-2). Beyond this, God loves us and gave Jesus life for us when we were still enemies (Romans 5:8). We serve God not only because He is the ultimate authority over all things, but even more, because He loves us and wants what is good for us. So, it is better to die in God's promise than to turn back to Satan's powers.
You will notice that I have not tried to teach that ancestors, evil spirits, and witchcraft are not real. First of all, Jesus himself talked to demons and Satan, so evil spirits are real. They have real powers and are able to harm if God allows it. Second, I cannot always discern the difference between Satan's power to harm or his lies. It is certainly possible that he is using a witch to accomplish his desires. Whatever power he has, he could use a witch as his puppet to demonstrate that power. So, I cannot always know whether witchcraft is just a lie or Satan is really acting through it.
For example, there is a witch who claims to be able to travel to New York on a flying carpet in 30 minutes. That is obviously a lie, there is no way a person can travel on a flying carpet that fast . However, when a person who has a real disease goes to a witch doctor and comes back cured, what has happened? Perhaps, it is all a trick. Or perhaps, that person has really been cured from a physical disease. The difference does not matter because in each case that person is being trapped by Satan's power or lies.
You might also notice that in the Old Testament, God did not always confront the fact that false gods are not really gods at all. When the Israelites were in Egypt he did not tell Moses to teach that the Egyptian gods were fake. Instead, he demonstrated his power over them. Each of the ten plagues is directly aimed at one of the Egyptian gods. The plague of darkness showed that God had authority over Ra. The death of the firstborn showed that God had authority over the Pharaoh himself (who was considered the embodiment of the gods). God didn't confront the fake gods with words, instead he confronted them with power. From the Israelites perspective God defeated all the other gods. He truly had all authority and was the Most High God, the only one deserving praise and worship.
Whatever the Kaonde understand about witchcraft and evil spirits, it is vital they understand that God is the ultimate authority and deserves our loyalty, no matter what God allows to happen to us. We will all die one way or another, but only God can forgive us and save us from hell.