The 4g issue could be your area (tower area) you should contact Sprint and see what they say. All else fails, try a factory reset and see if that clears the issue.
Please note, this is the Motorola Backflip ROOT area; since the mentioned phone is not a Motorola, or a backflip; that the backflip does not work with 4G and that your question is not a ROOT question, please post questions like this the correct area.
Good luck BTY