Pathetic customer service

I emailed computershare with an instruction to update my banking details with all the relevant documentation, i.e. ID, instruction letter, proof of banking details, etc. The banking details on the system was then updated with the incorrect bank account number (digit missing). I logged a request for them to fix the incorrect bank account number as they have all the relevant documentation almost a month ago. To date, a month later, my banking details has not yet been updated. When I called the call centre agent advised me that it usually takes 7 to 10 business days to update but the department currently has a back log and she cannot tell me when THEIR error will be fixed. I find that totally unacceptable. A dividend which is due to me now cannot be paid and they cannot tell me when they will fix their own error.