FNB blocked my accounts for no reason

I tried to use my fnb debit card at checkers to buy groceries and my card kept declining and a supervisor told me that my card had been blocked.I was totally shocked and felt like a ********,other customers looked at me as if i was using someone elses card.When I contacted FNB call centre I was told that my account was blocked due to not submitting a self confirmation form.This form is to state that you are not a resident outside of South Africa or conducting business overseas,both of which im not and im a South African citizen.When Pat Mokjope from the CRS department at FNB contacted me she could not give me an explanation as to why for something so trivial my account would be blocked and she said that their system sent me an sms on the 23rd of October and the 6th of November requesting for the documents.I went through my phone and no communication was sent to me,how can they expect an sms to be the way to communicate with a client, to be so reliable for something that was so important,instead of them phoning me. I was inconvenienced with my time and my reputation and I had to go back to Checkers to prove to them that I was good for the transaction after FNB unblocked my account.Imagine if it was an emergency and I was away from home and this happened. Is the way FNB treat a loyal client for over 20 years and I opened other accounts also with them.I wonder if others also faced the same ridiculous treatment.I am considering on closing my accounts