I am on my 3rd replacement phone from T mobile for this issue. My original S4 worked great for about a year then I started having a black screen issue where the screen would go black and I couldn't access anything. Was a huge pain, especially when a call was coming in and you couldn't swipe the screen to answer it!....but that's another forum.......in the midst of my trying to swipe the screen I dropped the phone and cracked the screen. I paid my $175 insurance and was issued a refurbished S4. Within 15 minutes of turning it on, I received the sim card error after re-booting, I found that I was having the same black screen issue!. I took it to the T mobile store. They were all puzzled by the issue, as they had never heard of this happening. gave me a new sim card and sent me on my way. I shopped a little in the same mall and sure enough, the sim card error came up again so I went right back to the T mobile store to show them the error message. They rebooted the phone and then called it to see if the black screen thing happened and it did. They immediately ordered a replacement for me. I got the replacement about 3 days later. This phone would not connect a call. It would dial and then just end the call. If I had an incoming call, I would answer, but there was no one on the other end and then it ended the call. I called myself from my home phone and it just went to voicemail, so I called T mobile and they set me up with a nice tech who said that he would report the issue and it may take 72 hours but that he would get back to me. At that point I went back to the first replacement and used that phone because at least I could make and receive calls! I just had to keep rebooting it because of the sim card issue! Finally replacment number 3 arrived from UPS, (My UPS guy said to get an i phone!)
I turned it on and with 20 minutes the sim card error came up! I marched, myself back to the T mobile store and they were so apologetic! I will say that inspite of all my issues the people at T Mobile were extremely professional and very apologetic.I am very happy with their customer service staff! They called customer support who told them that it is a known problem and that they are working on new software to fix it but for now to try a new sim card again and that if this didn't correct the problem then I would have to get a different phone altogether. The CSR at T Mobile told me the minute it does it again, and it will, call them because they have to give you a different phone because this is the 3rd time they are replacing the S4. Within an hour, the sim card message came up. I called T Mobile and they advised me that there was nothing more that they could do and that they would payoff my balance for the phone and give me $150 towards an upgrade of any new phone I wanted. So today I am heading back to the T Mobile store to get a different phone. I loved my original S4 until the black screen thing happened. My husband has one also and his has never given him any trouble so now I have to decide do I go with the S5 or try something else. So anyway, after this long story, Samsung IS aware of the problem but they don't have a fix for it yet. My advice is, if you can exchange your S4 for something else, do so because any replacement phone they send you will do the same thing.