Actually this is a NOT a scam! I got the same text message saying from St George bank, and it was them detecting suspicious activity that really did happen. I called St George and yes they do send these texts, and also from Westpac they use the same number. I should have replied that it was fraud, might have stopped them from getting away with $400 of my money :(

See my messages re St George Bank. At first I thought it was scam. Then I called St George and confirmed that it was their SMS. A Canadian telco company attempted to withdraw $869.88 from my account at 4.11am. Bank send SMS at 4.12am. Although I did not respond to the SMS the bank stopped the transaction going ahead as it was unusual one. There is no point calling the number the SMS was sent, instead call the bank.

In addition to earlier two comments, St George recommended that i do not use my card until they issue a new one with different numbers as the current is now compromised.
It appears they (the banks) do the right thing and the SMS was definitely not a scam.

Received SMS at 4.12am today saying:
St George alert: Transaction blocked on card ending (and my last 4 digits) at 'ROGERSWL 1TIME' for $869.88 at 4.11. If genuine reply 'yes'. If fraud reply 'no'.
I've checked my accounts and alerts and this definitely is a scam.

Received following message:-
Westpac alert: Block placed on card ending *** for suspicious transaction at 'STOP & SHOP 0852' for $299.05 at 4:00. If Genuine, reply 'Yes'. If Fraud reply "No'.

Definitely a fraudulent....

I want to know who chase these bast**ds and make them accountable???

what did they say, I have this number on my account that was called from a hacked mobile account

Spam. SCAM. DO NOT ANSWER.