overcharging with bank fees

I am extremely frustrated with FNB forever charging me for everything , no one ever explains to you the amount of bank chargers you will receive, I have an investment account which is scheduled to run at the end of every month but im getting smses saying that transaction could not be processed which is bull because there is money in my account and the same investment account where I had a R100 but all of a sudden I have a negative balance and I didnt even use my account and 2 days later my cheque account gets charged R15 for god knows what and my whenever I buy airtime using cellphone banking the airtime at times takes too long and ive had times when I had emergencies but the airtime took forever to come through I am sick and tired of fnb and I am seriously considering cancelling that account.they seriously need to stop over charging their customers.