Debit order date not changed

once again Cell c promised to change my debit order from the 21st of each month to the 25th in december. January the 21st cell c debits and my bank charges me a return fee of r230. Called the call centre last week would advise me they will sort this out. ref ***. Cell c has yet to come back or refund me. What is happening with the level of service and who is taking responsibility. This is time consuming to post these complaints.