Thanks so much guys. really do not know Double Spend can do this. but really such feature does not make good to me.
replace by fee feature is Ok and helps when you want to accelerate confirmation. this double spend..whats the benefit ? only good for cheating or ?
It was a
replace by fee and he has done it with the first transaction which was to the address A in my example. But since the other transaction which gone from address A and the input of A which is the output of first transaction was changed hence the tx that was to you was dropped.
The idea is a miner needs to pick up the transaction.