why do they pick up the phone and with out saying anything just hang up

To busy yo deal with phone calls.

To maintain the standard Walmart/Sam's Club experience, of course

It be to busy up in the store with to many of the customer

Possibly can't hear the incoming calls.

Easy zero help overwhelmed

all walmarts in the area do the same or just dont pick up at all.

I guess they're really busy, perhaps?