Act 16:16
And it came to pass, as we went to prayer, a certain damsel possessed with a spirit of divination met us, which brought her masters much gain by soothsaying:
Act 16:17
The same followed Paul and us, and cried, saying, These men are the servants of the most high God, which shew unto us the way of salvation.
Act 16:18
And this did she many days. But Paul, being grieved, turned and said to the spirit, I command thee in the name of Jesus Christ to come out of her. And he came out the same hour.
Look at how spot on accurate this demon spirit was in what it said, just like the demon spirit who impersonated "Samuel" through the mouth of the diviner/soothsaying woman at Endor.
Thus, if one wanted to argue that spirits always lie, we have two cases in point where they tell the exact truth. A third case was Satan telling Eve "You shall be as gods knowing good and evil". The trouble is you don't want to be as the demon gods knowing/experiencing evil whereas up to then Eve had only known good.