Pathetic Customer service!!!

I have had my cellc contract for over 6 months, bill always paid on time. In March i changed bank accounts and closed my account the debit order was set with when i called cell c to notify and add my new banks details as a debit order they advised me i can't do that as my account was less than 3 months old and advised me to pay manually which i have been doing since March, i manually paid my bill on time every month however today i find out that there is a R70 penalty added on my account due to a debit order bouncing as the account is closed just like i informed them back in march. Now I'm told i have to pay the penalty to use my contract sim going forward which is ridiculous. This is a fault on cell c end as my payment was done and they was notified to cancel that debit order back in March!!!