Due to the increase of iPhone theft something needed to happen to prevent this; hence the Blacklist was created. Mobile Networks were able to add the IMEI number of an iPhone to their Blacklist and deny access to their network.
There is a way to remove an IMEI number from a Blacklist: The service is called IMEI Unbar/Unblacklist Eligibility Check. that can find all avialable unblacklist service specifically for your iPhone.
It goes without saying that anything else than a CLEAN result is dangerous.
You do not want to purchase an iPhone that has been reported as LOST, STOLEN or FRAUD, since not only you will have issues operating it, but you might have issues with the law!
A Blacklisted iPhone means that it cannot operate with a specific network and inside the whole country that it got Blacklisted. Avoid purchasing an iPhone that has any of the Lost, Stolen or Fraud values.
As with all products, it is very crucial to avoid purchasing one that it is Lost, Stolen or acquired through Fraud activities.
The same goes with iPhones, so it is very important to perform an IMEI Blacklist Check BEFORE buying one.
Apart from the fact that you might get in trouble by buying a Blacklisted iPhone, you will certainly have problems using it with a large number of Carriers.
In case you purchased a Blacklisted iPhone, there are still some solutions:
If you do not know the Blacklist Carrier, then proceed with an IMEI iPhone Blacklist Status Check to find out and learn if you can Unblacklist it.
If you know which network blacklisted your iPhone, then the iPhone IMEI Unblacklist Eligibility check will tell you if an unblacklist service is available and redirect you to it.