Unhappy clients

Am very unhappy with FNB I had and overdraft with them earlier this year they sent a collection company and I paid the full amount, they promised paid up letter till today they haven’t and I have been going to FNB to report this but this letter it’s not being solved. Ever since I been getting calls from different collecting companies and I been telling them the same story and also sending them the same proof of payment, honestly this is bad *********** service.