I've dealt with this issue ever since I bought this phone - and would rather throw it across the room and watch it burst into 1,000 pieces than have to see the error pop up
again. All I did was cut out about 1-inch by1/4" inch strip from a postcard - or any heavy weight paper. In other words, not cardboard, but not copy paper. More like the weight of a vhs cover box, cereal box, etc. I inserted one end of the strip above the sim card
and below the phone shell (over the part of the sim card that's not showing); and folded the rest of the paper strip (might have to tear some off) to be double ply above the part of the sim card that is showing. Put on the cover; you should have to press firmly to get it to fit on and smash the double-ply strip down. Make sure the double ply is only over the sim card, not any over the battery. This worked for me!