Well, I can pretty much guarantee that none of them will be licensed in the state.
Payday loans are under SC code 34-39-110. License is required, just as is the holding of a paper check.
http://www.scstatehouse.net/code/t34c039.htm
Limit of $300 loan, interest of 15%. No other fees allowed. I don't know of anyone online companies, except paydayok, that charge only 15%.
The companies operating without a license in SC could be charged with a class B misdemeanor, fines of up to $1000 per incident (per loan, per overcharge of fees)
I would also file written complaints with your state attorney general and dept of consumer affairs. They can file suit against the companies, if enough people complain.