The Time Heist was a plan. They knew in advance they would be bringing people back. Since New York's sidewalks weren't covered with cell phones, they knew that cell phones went with the disappeared, and would presumably come back with them.
At the very least, they would need to reactivate communication services for team members who had disappeared, such as Nick Fury, Maria Hill, Sam Wilson, Wanda Maximoff, etc. so they could be summoned ASAP if needed.
So it wouldn't be far out of their way to do it for Friends and Family also.
No doubt it was one of numerous administrivia details that Black Widow either did, or delegated to Stark staff.