I like the idea, but the way you have suggested it, thematically doesn't make a lot of sense.
If Character A reaches level 50, everyone should trust that character, but why then would Character B, a lowly level 1 get trusted automatically?
I think it could be a character thing certainly, all future stuff that character does, in Ooroborus or otherwise should just get an auto call feature.
Account wide is a good idea too, but I think it would have to be implemented slightly differently to give it the right thematic approach. Or make it something like a vet reward or something along those lines where it is more for the player than the character.
"Where does he get those wonderful toys?" - The Joker
I think it should be standard, Not a reward.
-Rachel-
You've played your first character to level 50.
You've successfully unlocked the Epic Archetype on a given side.
Presumably, in order to get to that point, you've done enough content in the game to have earned the trust of every single contact you've helped, so why not give this as an account-wide power? For lack of a better name, let's call it Implicit Trust.
The way it works is simple:
When introduced to a new contact, you speak with said contact, run the first mission they give you and you INSTANTLY get the ability to call them. No more mucking about running all over hell's half-acre, from missions to contacts to new missions and back again, until 3/4ers of their @#$%^& arc is complete before they trust you with their cellphone numbers! Everyone, from level one contacts in Atlas Park all the way up to contacts in the Shadow Shard, they all inherently trust you with their contact information after running their first mission.
I'm frankly kinda surprised this wasn't given as a vet reward already. Woulda beat the crap out of Greek Letters as chest emblems.
Whaddya think?