I can't get an LTE or anything other than H on my Verizon LG G4 on AT&T, why is that?

[AC Question]

I cant get LTE or anything other than H on my Verizon LG G4 on AT&T

I have an unlocked Verizon LG G4 VS986, I have an AT&T sim card in it and can make and receive calls and texts just fine. I also have internet but it's showing the H symbol and an up and down arrow below it. I have speed tested it in many places including my house and it is slower than My At&t s6 edge was while using the data. I checked a bunch of places and the APN settings seem to be correct. Why am I not getting 4g or lte speeds when I was in the same places with my At&t branded S6 Edge? Can anybody help me atleast get hspca or lte?

Thanks