Recently I traveled to Japan and had to get a SIM card. When I came back home and installed my original SIM card I was stuck on 3G and the 3G didn’t work. A few weeks later it starts working but it’s still on 3G and I randomly don’t have any internet at all.

I recently went to my SIM card supplier and checked what could be wrong and there they said they didn’t know what could be wrong so they sent in my SIM card to get checked and I got a spare one. The spare one was also stuck on 3G but it does not work.

The issue seems to be with the iPhone and when I look online I can’t seem to find any fix to this.

Any help would be greatly appreciated!