Unlock iPhone4/4s to make compatible with gov. sim card?

Aug 18, 2018
How do you unlock an at&t iphone4/4s to make it compatible with government sim card? Please help?? I've been trying to fix it for about a month now and I still can't figure it out.. I'm afraid I'm going to lose my government service if I don't figure out something really quickly!!
Can anyone help me with this please??