Android phone my dad has medium end sumsung j7 dual which gives option to use one sim slot in 4g and other in 3g as 3g is available all over the world but 2g bang has doomed this means you can’t use second sim slot in developed countries even in New York at and withdraw 2g bands which means I can’t use dual sim with 950xl as it only allows second sim to be in 2g I don’t know it is a hard ware or software that we can fix but both sim slot supported 4g in 950xl but when on dual sim one high speed and other at 2g basis as it only allowed this option.