My betta's been alone for months, and he's happy as a clam! :) The only company a betta needs is you, my betta watches me all the time follows me around :) If you really want a tank mate, you can try snails or shrimp in your fish tank.
Petsmart should take the fish back, I've heard of other people taking back fish on this site and getting their money back.
Have you got the Nitrogen Cycle going in your tank or do you just have a filter in there? Without setting up the nitrogen cycle, the filter will not keep the water clean. Fish don't urinate like people do, the excrete ammonia through their gills when they breath. You can't see the ammonia and you can only smell it when it has reached toxic levels in the tank.
Here's a guide to setting up the nitrogen cycle if you haven't done this already.
You can use the drinking cup to get out the water if your tank is cycled, no special way to do it! :) And they do have tank vacuums, You can use it to suck poo out of the gravel in your filtered tank.
If you haven't set up the nitrogen cycle, you will need to do 100% water changes every 2-3 days manually to keep your fish happy and healthy! :)