Disappointed in my bank

I always talk about FNB to my friends and family as I am impressed with FNB as I have never had any problems. But my opinion of FNB changed recently... On Friday the 15th of September I tried to purchase Vodacom data online, I confirmed the purchase on my FNB app as requested but the online banking screen after confirmation stated "transaction unsuccessful", it was due to some missing "link". As it is human nature to try again i tried purchasing the data again and it gave the same error. I then tried the transaction on my FNB app but it was also unsuccessful. After a short while after all these attempts i got a notification that all the transactions went through after the attempts. This means my bank account was deducted with all those attempts. I did not budget for this amount of money to be deducted from my account for data purchases. I feel it is not fair that i am out of the pocket for a transaction that initial stated "unsuccessful". I did email a complaint but till now have not received a reply.