When Scott Lang goes to the supposedly SHIELD base to steal Hank Pym's prototype of a signal decoy, he finds out that it is now an Avengers' building. Falcon arrives as soon as Scott lands on the top of the building.
Scott Lang: Alright I’m on the roof of the target building.
Hope van Dyne: Somebody’s home, Scott. [just then Sam Wilson in his Falcon flies in]
Voice over Radio: [on Sam’s radio] What’s going on down there, Sam?
Scott Lang: It’s the Falcon!
Sam Wilson: [into his radio] I had a sensor trip but I’m not seeing anything. Wait a second.
Dr. Hank Pym: Abort, Scott! Abort now.
Scott Lang: It’s okay, he can’t see me.
Sam Wilson: I can see you.
NOTE: I recently read somewhere online that Sam was on comms with the Black Widow, which, I don't think is true. Because it wasn't a female voice on comms (let alone Scarlett Johannson's).
So who was on the comms talking to/guiding the Falcon during this heist?