Later Stage Networking Advice

Go to hypw with 3.9+ and strong resume (multiple leadership roles, relevant clubs and skills, etc). Been doing great with networking with certain banks (GS, Jefferies, CVP, SMBC) and already have referrals secured for some, but genuinely just haven’t been able to get alumni on the phone at MS, Barc, Bofa, and Gugg (though the latter two admittedly have less). Sent follow ups across the board with very little luck. I’d really appreciate any advice people have about how to maximize remaining networking time before apps open as well as whether and how to network once they do. Thanks!