FNB Credit Card Service

I have had a really bad experience with FNB they blocked my credit card, they asked me to pay an amount I paid that amount but everyday now at midnight my credit card get blocked again. I have to call the bank every morning and they unblock it. I ask them to explain the process to me and they say I should speak to the collections department. The collections department acknowledge that I don not owe anything now as the required minimum payment has been made but they cannot help me to explain why my account is getting blocked everyday. FNB is becoming abusive to me as a customer and I am unhappy. If there is anything else owing it does not show on my banking app but still my credit card gets blocked everyday. No one at FNB has been able to explain why or to rectify this.