missing money

On the 8th April my number was hacked and this person was busy using my number whatsapping people asking them for money. my Colleague was also sent a message by this person asking her for money.She sent R900 and my mobile app notified me that there was an incoming 900 I then immediately transfered that 900 to my mother which she then later transfered it back to me.When she sent this 900 back it affected her balance .The 900 that I sent to her did not go in her account cause balance is now less than what is suppose to be excluding the 900.This matter is being handled Thabo Lebese and I have explained this to him but he won't listen and ask for facts of my story.

Can someone from FNB explain what happened to the 900 as it can't just vanish.Camparison to be done on her statement.