I bought a carrier unlocked iPhone at Best Buy a little while ago. It worked in the US with Tmobile for a short time. I then traveled to Costa Rica, where when I put the SIM card in, it wouldn't work. The message was the SIM card wasn't supported and to contact my carrier. Applecare said there is nothing stopping it on their end but didn't suggest any solutions. I went to youtube and found a variety of videos and realize that it needs to be unlocked. For this, I saw a lot of services, all around $100 that offered to help the unlock process. Can I do this process myself without paying or is it necessary to use those services? If so, I wanted to see which one(s) are the most recommended to use in this forum.