Excuse me, but that's not right. Saul asked Samuel what he (Saul) should do. There was no mention of any intercession. Saul conjured up Samuel to tell his fortune, pure and simple, and that's the definition of necromancy. You're inventing Scripture to trash Catholics when you claim that Saul asked Samuel to intercede for him. He didn't.
I will concede that you're partly right. It was because the Lord wasn't answering Saul that Saul sought Samuel out (2 Sam 28). This isn't intercession. However, I would point out that Samuel chastises Saul for asking what will happen of him rather than the Lord. The point is that if your not right with the Lord, at least well enough to pray to Him, then there is no point in seeking anyone else out.
If you want to say I'm trashing the Catholics then fine.