Check any Sprint or Boost Mobile iPhone IMEI to see if it's clean, blacklisted or has an unpaid bill.
Sample results:
IMEI: 352002****38701 Model: IPH 5S GLD 32 VMU BOX SGL Model Number: 885909728039 Manufacturer: APPLE, INC BLACKLIST STATUS: CLEAN (FAILED DEACTIVATION) SPCS: YES Activation: NO
OR
IMEI: 35382****127919 Model: INS IPH 7 BLACK 32GB SGL Model Number: RECIN732GBK1 Manufacturer: APPLE, INC BLACKLIST STATUS: UNPAID BILLS ICCID: 89011201000488102599 IMSI: 310120148810259 SPCS: NO Activation: YES