Extremely high and ridiculous bank fees

I am furious with FNB, I used my card to tap n pay for items at one store. This store did not bank for over a week now my account is sitting in a huge negative because of it. I have been billed R120.00 for each of these transactions by FNB for the insufficient funds fee. I find this highly unfair as it is not my fault the store did not bank sooner and now I am carrying all the costs. I feel it is unfair to charge someone R120.00 in bank fees for a R30.00 transaction Most of these are small amounts that were not banked and my bank fees cost more than what I purchased. So far I have about 8 bank fee charges this month alone of R120.00 each. This is absolutely ridiculous. FNB please sort this out, I have tried speaking to customer care but they are not interested or cannot help