About one year ago, I switched to PlatinumTel's PayGo service (https://www.ptel.com/plans) which includes talk, text, and 4G data. At that time I had my phone, the Optimus L9 P769, unlocked by T-Mobile. Everything worked well.
About two weeks ago, the data stopped working for some reason. I use data very little, so I didn't mind. But now I am donating my phone to a relative who never owned a smartphone. I tried everything I could to fix the data, from adding PTel's APN to installing kuma82's locked bootloader ROM. Nothing worked. I suspect the part of the phone receiving data broke after I dropped the phone. If there is any way to verify this, I would be happy to learn.