1. What does it mean if I have a bad ESN? A bad ESN means you can't activate an iPhone on your current carrier. For example, if you purchase an iPhone with a bad ESN from someone who used it on Verizon, then you won't be able to activate that phone on Verizon.
2. How do I get a bad ESN? You can get a bad ESN three ways: reporting your phone as lost or stolen, if the phone is still active on your wireless account or if you have an outstanding balance on your account.
3. How do I make sure I have a clean ESN?According to MaxBack, make sure your phone is completely off your wireless account before delivering it into the hands of a new owner. Settle any outstanding balances as well. You can see if your ESN is clean through a check on Swappa. It'll let you know if the ESN is activated on an account or not.
4. What do I do if I bought a phone with a bad ESN? An ESN can only be cleared by the original owner of the phone, so you would need to contact that person.