Every single pet store/fish store I have ever been to in my 18 years of living have allowed returns or will accept fish back if you need to give them up. I also don't believe you don't have any Petcos or Petsmarts relatively near you. We have THREE Petsmarts nearby, a LFS, and TWO Petcos. And I live in an incredibly small down that isn't even marked on the map.
If you can't bring them back or give them to a fish store, ask your friends if they could take one, or see if your parents would post a craigslist ad for them. Give them away for free, if you have to.
I know from experience not to listen to most Petsmart employees that say what housings you should put certain fish in. These are the people that often say a .5 gallon cube is an appropriate living space for a betta. When my sister got her first betta fish, they recommended a 1 gallon tank with a divider and offered another fish, and said heaters weren't necessary. I'm just saying not to always listen to what they say, and listen to those on this site instead. The people on this site have had bettas for years and actually know what they're talking about.
Either get dividers or rehome them, or they will kill each other.