Are those said not valid transactions are you really did it with your accounts? You remembered that you did those trades on their exchange?
This is my firstime to heard this kind of problem on a exchange.
And, this thread should be in Scam Accusation, just move the thread and let's hear some opinion of others and maybe there are some bitcointalk account owned by coinsbit.
I can not believe that the exchange interferes with the trading of traders. It seems to me that physically they are not able to track all transactions. Imagine how many operations this happens every minute.