This is a real problem in a game with a dense, very large, three-dimensional urban environment with no true "centres". You don't have villages or settlements like in other games towards which the player will naturally gravitate: it is one huge environment with details around every corner.
Social Hubs exist in multimillion inhabitant cities in meatspace. Cultural venues from opera houses and theaters to fringe group underground venues, bars, cafes, restaurants, ...
Think the bar of Jackie's mother, where you had some encounter and quests starter.
In Cyberspace you have/had BBS, mailing lists, groups in messengers, SM-applications, fora and so on...
These would feel more plausible than just receiving a call, when being near to some location in what is felt more than 95% of the time.
Mercs will attend some bars and clubs selectively (After Life, e.g.) or have meet-ups with their clients (Peralez, DeShawn e.g.).
The Cyberspace aspect was even more neglected.
Shards and phone calls are ok, but during quests or mission sometimes add meatspace/Cyberspace meetings to increase "involvement.