[Q] Microsoft lumia 535 windows fone 8.1 network problem topic

hi anyone please help me with this network issue I'm having on my Microsoft lumina 535 windows fone ... each time I try to switch to 3G network from that "highest connection speed" menu , it displays 2G network instead of 3G and I've tried all other sim cards ... it saysthe same thing and iI've been using edge network which is very slow so please can any expert just give me a code to force 3G network on ... I'm using windows 8.1 by the way and I've tried using that ##3283# code .. it wasn't working so idk if there's any other I can use to force 3g network on .. many thanks