Unexplainable charges

On the 5th of December 2015 i did a transfer of R250 from my pocket account into my business cheque account and then after that it said my available balance is R350 then after that I went to Debonairs at Southgate and I swiped for R179.90 and then i got an email that said R179.90 has been reserved and my available balance is R170. After that I went to Sheads Southgate Meat and I swiped for R148.90 and once again I got an email that said R148.90 has been reserved and available balance is R21. Now on the 10th of December I was charged an amount of R145 and when I asked I was told that it is for the amount that went of from Sheads cause when the merchant banked the money my account didn't have money, now i don't understand is that the email that I got on the 5th is said the money has been reserved. and before I purchased I checked my balance in fact I did a transfer so that I can accommodate all my purchases so i honestly don't understant why am i being charged R145 for something that is not my fault. I need someone to explain to me why i must pay for mistakes that I didn't cause.