Flight numbers 1328 and 3828, hmmm.
And they way they say it,
thirteen-twenty-eight and
thirty-eight-twenty-eight. Hmm indeed! The pace of ops at MDW can get such that people start stepping on each others radio transmissions all too often. Is it possible that an airline pilot has to concentrate on the flight number since it changes all the time and since the company call sign is always the same, maybe some don't even hear it?
Whatever the reason, it's a cheap lesson for everyone.