How to reflash 868

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How do I reflash the 868? I know how to put the phone into testmode, but I don't know how to reflash it. (I don't have any flasher software). That would solve the problem with tampered!, wouldn't it? Why does the phone put itself into tampered! mode?, I really would like to remove that. Now my phone is completly useless, because it's tampered! I really don't know how to detamper it, perhaps reflashing it would solve the problem!

any help greatly appreciated
thanks
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