We generally call that “necromancy”, and people use that to also contact dead family and friends, cats, scientists as well as occultists.
I’ve seen posts over the years for this but they’re hard to find, so have a browse of the necromancy category while you’re waiting .
Personally I work with a dead mage I call Akash. He was an Ancient Egyptian priest about 6000 years ago - by my UPG, of course. (Unverified Personal Gnosis), and a witch I call Emily, who came to me claiming to have been murdered by someone I know, and who wanted to help me learn her style of witchcraft. She wasn’t done, and gets to continue vicariously through me.
I made a permanent portal for her following the necromantic work of the Sorceress Cagliastro in her Blood Bible volume II book. For Akash I created a fairly normal vessel out of a statuette.
THEY contacted me though, I called Akash expecting something else, and met Emily while astral traveling to a location that happened to also be where she was buried. I found her shade tried to that location and provided her a way to leave it. I am a psychopomp and tried to help her move on, but she wasn’t having it and now we’re friends.
You have to be sensible and use your discernment with all of them. All ghosts are hungry and need to feed, usually vampirically. The mages may have found stable sources that are not you.. The ascended and higher beings do not.
For the non-famous, I feel there’s lower risk as there’s no “big name” to drop for a imposter to pretend. People are people, whether a non-human entity, or a human without a physical body, they al have thier own agendas, expertise and goals. It depends what you are up to.
Damian Echols did an interesting video on one form of mage immortality that requires feeding that I saved here:
Damien Echol’s video paused at the point of describing how the Egyptian created vampires:

The paranormal world
What interesting about this, is the whole thing looks to me like a missed opportunity.
If I didn’t just add 2 and 2 to make five, we know an advanced Egyptian mage, who is motivated to talk to occultists, and yes, he’s a tricky, lying, parasitic ghost who will try to suck you dry or bodysnatch you, (I guess he not called the “Subterfuge” for nothing) but what has he seen and what does he know? He’s been hovering around humanity for 1000s of years. Unlike the Goetia who to me a are a bit high minded, he’s seen it all up close and personal, and can relate to us as humans.