Welcome Mert, good to have you here.
I received a warning for betting under the minimum about 2 years ago. The problem may have been the cancelling of the original bet I think, as that is what a lot of posters were saying.

IE:
Place Lay bet for $5 @ $1.01.
Up that stake to $6.
Betfair then shows 2 bets, 1 for $5 and 1 for $1.
Then adjust the $1 bet up to what price you would like.
Then cancel the $5 bet.
Presto, on for under the minimum.

__________________
Jose'.