Can't make or receive calls

Okay, so I bought a lg g4 h635c international phone and it does have the bands for lte in the US. When I go to the hidden menu to select the band it will tell me success and show 4g at the top. When I try making a call, it automatically tells me "call ended". What is the issue? I have racked my brain off and can't figure out why its doing this. My husband has the same phone and his does this too, so I know its not a network issue. Is there specific settings my phone should be on. I am using Straight Talk and with the sim inserted it automatically connects to hspa +.