Hey there, joe1994! I am so sorry to hear of your issues with your G6! I've had mine for a few months now and I've been pretty happy with it, I feel like the camera was a little smoother in previous incarnations of the G-Series (and I was in love with that sick camera attachment for the G5) but overall, I've had pretty good luck with it. I'd love to try to help if I can.
Did you notice the issue start after the Oreo update back in June, or has this been ongoing since before then?
I'm sure you've already gone through the steps here: Battery life: LG G6 and I know you said that you've completed factory resets on the device, but have you wiped the cache partition? When you run the factory reset, do you have it automatically restore your apps from before the wipe? I ask because there may be an app running in the background that is eating up some battery life and you may not even realize it's there. Are you running any third-party battery saving or cleaning apps? I'd definitely check the app usage: Settings>General>Battery>App Usage. Also, if you do have a battery saver on, did you check your exclusions to make sure that something is not sneaking passed the power saving mode: Settings>General>Battery>Power Saving Exclusions?
Please forgive me if you've already explored these steps!
Finally, when did you purchase the phone? Was it less than a year ago, or do you have insurance? Is there any damage to the phone (cracked screen, excessive wear to case, moisture damage)? If you are still within your year, or otherwise have the extended warranty allowed through your insurance plan, you will be able to file a warranty exchange through T-Mobile by calling care at 611 or 877-746-0909 (for post-paid), reaching out to your Messaging Expert by clicking the Message Us button, or contacting T-Force via Facebook or Twitter.
When you reach out, they will want you to complete troubleshooting; you'll just need to explain that you've already done so up to and including a factory reset. This is the last step in almost every troubleshooting flow and the natural next option is an exchange, if applicable. Good luck to you!
I am just going to deal with it for a few more weeks. At the end of month I will getting home and switching to project FI. Besides coverage issues and dealing with this piece of junk phone, I have nothing bad to say about T-Mobile.
Ah, I gotcha! Best of luck to you then!