3v3 ranked twisted treeline

Me and my friends just played our promos in 3v3 ranked we are all silvers and we won 4 of the 5 games and we get placed into bronze 3.What is that bull we win 4 of the 5 games and we get placed to a lower state of ranked bronze 3.Now I know its not just me who gets this problem to me that makes no sense we win 4 games in a row just to get placed into bronze 3. Fix this please