Incorrect missed payments on my account

I have had an account with this company for over a year going to 2 years now, my monthly debit order goes off without fail every month on the scheduled payment date. 4 times they have listed my account on the credit bureau as that i have missed payments, when i call their offices and they check this they confirm that i have never missed a payment but still continue to list my account as missed payments on the credit bureau. Every account listed as a missed payment reflects negatively on my account, i have made numerous calls and sent countless emails which they state they have on their files but in 6 to 7 months that i have been attempting to address this matter not one person has called me to update me on when they intend on removing this missed payments from my credit history and as to how they will prevent this from happening going forward. I will now be taking legal action as my complaints are obviously being ignored.