Only IMEIs with Status showing [SPCS: YES], are supported. Prior to submit check your IMEIs on the:
Sprint USA iPhone Blacklist checker (Official check)
and put the check result in the Noters field!
The service will turn your Unpaid Bills SPCS: YES IMEI into Clean IMEI.
This service will not unlock your iPhone, it will only change status of device from Unpaid Bills into Clean so you can unlock on Clean IMEIs unlock service.