I was thinking of ways to try and break the contact between the two antennas earlier and I had a simple and somewhat dumb idea. Sticky tape/ Sellotape, whatever you want to call it. I cut a thin strip to make it look a bit neater and I'm 100% genuine that it works for me. A couple of times I managed to make it drop 1 bar but I don't know if that was just a normal strength fluctuation, or possible my hand making the connection to the underside of the iPhone. I figured it's worth a shot if you're not into cases and "bumpers".