FNB 55 days interest free FALSE ADVERTI*****T

FNB 55 day interest fee account. I have been a client with FNB for many years, today I find out that I was charged interest on my account which I did pay over the minimum amount for that month. To still be charged interest evev being under the 55 day mark. After many calls and banker chats I was told that the 55 day interest fee is only for the 1st month of joining (false advertising). On the banker chat I was told that the account works 30 days spend 25 days pay back in full. Not sure what is the truth but definitely FNB is running a mock with there loyal clients.