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 and include employee names if you want. Also a manager name if you can. If you can't even complaining about the bettas period should do something.
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 service and when you notified the staff/employees of problems they failed to improve upon anything at all.
Anywho, that's how to get things done.
Hope this helps!