FNB Odd Billing

Made a purchase on Friday 7 August 2015 from Ackermans and received a notification of the transaction as well as my remaining balance. Bought lunch at Mc D's yesterday (and that was the only other transaction I had made) - this morning I log onto the FNB mobile app to find that my balance is R224 short. Now the argument could be that a few transactions had not gone through however if that's the case on the statement what's the purpose of the \balance"and \""available\"" amount? This is so frustrating!"""