My LG G4 had the infamous bootloop issue and LG's live chat referred me to Futuretel. They gave me mailing instructions, and I asked if I could bring it in personally and they said it was fine.
I brought it in on a Friday (as it turns out, you're not really supposed to but tons of people try to anyways). Signed a few forms, they explained to me about the $35+tax fee if it turns out that my warranty is voided. They said I should expect it to be fixed by Wednesday.
On Monday afternoon I got a call saying it was fixed and ready to be picked up! Someone else picked it up for me so I can't say anything about how well it works but they assured me if there's anything still wrong, I can message LG about it and bring it in again.
I was hesistant to bring it in because of the bad reviews but everything worked out well