Inadvertent Time-Out

[Jumpshooter40]

This happened in my son's rec league game last night:

Team A and Team B are tied with less than one minute remaining, with Team A in possession of the ball. All of the sudden, one official sounds his whistle and signals time-out to Team A. The Team A captain says he wasn't calling time-out, but was verbalizing to his players to 'come out' and that he didn't call a time-out and does not want a time out.

The official was set to just call it an inadvertent whistle and inbound at POI, but now Team B wants a time-out. Should this be granted.

In addition, are substitutions allowed during an inadvertent whistle?