[Q] Lumia refuse to take any sim card after enter sim unlock code from at&t

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http://forum.xda-developers.com – I got a sim unlock code from AT&T today. I took out at&t sim card and put in a t-mobile sim into lumia 900. It prompted me for PIN(unlock code). I keyed in unlock code for 10 times and the screen start to ask me for PUK. I entered the unlock code for couple more times and it still refused to unlock. Then, I kept on trying until I hit 32 time. Then my lumia 900 kept complaining about invalid sim. I put my at&t sim back to lumia 900. My lumia 900 still refuse to recognize the original at&t sim. I borrowed another at&t sim from my colleague and his card will not work on (HowTos)