hmm the cellphone issue i think i found a quote that could prove that cellphones can be used
Piper: That's ridiculous. I would never abandon you guys. If I had known I was gone this long I would've called or orbed or somehow let you know I was okay.
I'm assuming Piper ment the use of cellphones. So if there is contact to "up there" then contact should be available down in the Underworld. But I'm only assuming.