Here's something that might help:
Go here: PetSmart Store Locations for Pet Supplies and Pet Accessories | PetSmart
Enter your Zipcode then using the map find the store you shop at. Click the red icon representing the store. It will bring up three tabs. The default tab has the city name and store number. Ex: Melvinsburg #000
Copy that number and city name.
Next go here:Contact Us
File your complaint there. I wouldn't make it sound too nasty the first time. If it happens again you could kick it up a notch.
Make sure they know you're disgusted and disappointed with the care of bettas. If that doesn't work and you have to file a second complaint it wouldn't hurt to tell them you will contact PETA if they don't up the care.... Most lfs would do anything to keep PETA off their tails.