I bought an s21 ultra on offer up. Did my due diligence by checking IMEI And inserting my sim before giving him my money. So I contacted him told hin I wantedto buy and asked him if he could deliver as my car was in the shop and had no means of transportation he agreed an hour later he wasat my my driveway real polite kid must have been 18 or,19 years old, real proper and polite introduce himself and proceeded to show me the phone he took it out the case gave me the pen and said let me see your Sim . He put in the sim so we did that everything was fine I gave him the money and off he went, i headed it back inside did some chores, excited that I had a new phone I went back to it and to my surprisei I could not make a phone call or text I'm messed around with it I thought it was something with the SIM, I slept on it. so the next morning I did not do it in imei check as I already did one and it came out clean, plus I Was still able to surf the Internet watch Youtube videos so I will never Wood up thought that it was blacklisted, but for some reason I absent mindedly Ended up doing a check again t again and it was now blacklisted I'm assuming that it was reported lost or stolen after the fact. The website I would l Used did not tell me the reason why it was back listen. What website will give me thorough imei chech With reason that it was why it was black to even if I have to pay a couple bucks I don't mind. Also Also what are the proper steps I should Proceed to protect myself?