LG Stylo 2 (Cricket): Battery dropping from 98 to 0 in 15 minutes - help! How can I fix this?

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LG Stylo 2 (Cricket): Battery dropping from 98% to 0% in 15 minutes - help!

Hello,

I've had my LG Stylo 2 for one week and I've noticed that every morning after unplugging it from the wall charger, the battery indicator would indicate 98%.
Oh well, maybe it is the way it is..
Ten hours later, battery indicator.... 98%! Wow, that's a phone with GREAT battery life!

But today at 2pm, I decided to change the display brightness from 43% to 70%, and I put my phone aside while I was working. Then at 2:15, the phone was completely dead, and when I connected it to a wall charger, 0% was displayed.

I spoke with Cricket and they said since it's still under warranty, they could send me a replacement phone, but I would have to use the same battery - they don't provide replacement batteries and according to them, batteries are not covered by warranty :O

Please advise. I already performed a soft reset (power off, remove battery and SIM card for 1 minute, power on) and will leave it charging tonight. I wouldn't like to send it back to Cricket because it takes them 5 business days to provide a new one.

Thanks!!!