FNB blocks business account without any notice and explanations

Business account blocked with no reasons and no communications. We found that we're not able to do payments from the account - system was saying that the account has insufficient funds. It took over 3 hours and 12 calls to different hotlines to understand that the account was blocked by someone called Lucas. They gave us his direct phone (which was not working) and email, which he wasn't answering. It took another 3 days to find someone in the bank who can touch base with that person. As we understood, the account was blocked because of someone's complain. And that's it. No information, no communication from FNB - no SMS, no email, no call. Nobody was able to help (15 different people each one just referring to another department). The reason of hold wasn't provided. The complain wasn't provided. We've sent dozen of emails asking for clarifications - none of them were answered. We were requested for few documents, but nobody responded to them and nobody reviewed. It took another 5 days and 25 calls to attract some attention to the case. The hold was removed - again, with no explanation. And you know what? After a week the account was locked again - same way, with no notification and no explanation of the reasons. Is it a good way to serve your business customers? We can't risk our funds being stuck and our business to stop without even explaining us what happens.