cellc -refuses to help me to change a debit date

Cellc~ is one damn debit order date so hard to change I have being calling for the past 3 months and no one can damn help me I get paid on the last day of the month due to starting a new job , I visited the brance called 140 have e mailed but some how your'll can not get it right , now I got outstanding bank charges and going to be getting a bad credit rating due to CELLC .