***** ,always hide behind bank charges

I was very surprised to see my account had gone into minus .I checked my statement the amounts of R120 had been charged twice on the 12th of March and the 13th .Upon further inquiry I found out from FNB secure chat agent told me this was an honor fee .The amounts that where honored where R40 and R41 respectively .Now who in their right mind would rather pay R120 than just pay the R40 .Why did the bank allow the transaction to go through .why did they not decline. Now the agent telling me I should know how to track my money .Obviously I did not see that the account was in minus otherwise I would not have .The transaction was for Taxify but before you can get the taxi it checks your balance if you do not have sufficient funds it declines however on this day FNB deiced to honor the amounts my question is how? And if I knew this before hand would I not have just swiped for a more reasonable amount .Who pays R120 for a R40 taxi .Absolute nonsense