Have you tried to test the same SIM with a smartphone? What speeds do you acquire? Could you check APN settings your phone receives?
I would also like you to disable Auto APN and try a different APN set manually in Network -> Interfaces -> <Mobile_interface> settings: imovil.entelpcs.cl
You can also try changing LTE bands manually according to this example: https://www.youtube.com/watch?v=CAkjQ6a2qdc.