(Photo credit: Susan Law Cain / Shutterstock.com)

Every once in a while, carriers will try to woo subscribers from competitors through outright cash offers. If your mobile contract is up, you might want to see if you are eligible for a new phone via loyalty program (which means a new contract). Or you can switch to Sprint and get $400 in in-store credits if you will be switching from a competing carrier.

Now the promo has a few conditions. First, you will need to activate three or more lines under Sprint's Everything Data Share or Simply Everything Data plans. The line or lines to be switched over need to be at least 60 days old. Likewise, the $400 in-store credits can only be used for qualifying devices — these cannot be used for tablets, USB modems and other accessories.

Leaked flyers also indicate that the lines to be switched must not be from a Sprint affiliate, such as Virgin Mobile, Boost Mobile or Common Cents Mobile, which run over Sprints network. Likewise, the entire amount of the credit needs to be used in full. You will also need to sign up a new two-year contract.

The promo will run from today, August 19 through September 15. Check out the leaked flyer below (which we suppose will be available in stores today, anyway).