In case you're wondering, the line terminates without answering if you try to call it.
Lmao, Giuliani thought this was the number of a Trump official, because it's what showed up on his phone when the official called him. But it's not a real phone number, it's just a number that some outgoing Exec Branch calls show up as on the call logs. 
So Giuliani would keep trying to call this fake number, the call wouldn't work, and then he'd finally give up and called Madeleine Westerhout's line – listed as "White House Switchboard (Sit Room)".
Which means the "OMB number" is almost certainly Trump himself.
Which means the "OMB number" is almost certainly Trump himself.
Which means Sondland's August 9th call, immediately before he texted Volker about how "POTUS really wants the deliverable," would also be consistent with a call with Trump himself.
