try this
NPC Code:
if (playerchats && startswith(Unjail Player,#c))
{ tokenize #c;
if(indexof(#t(2),#s(server.jail))>-1)
{
setstring server.jail,#e(0,(indexof(#t(2),#s(server.jail))), #s(server.jail))#e(indexof(#t(2),#s(server.jail))+ strlen(#t(2))+1,-1,#s(server.jail));
}
}