Left Chubb and now charged again for work in Oct

Hello<br> <br> I left Chubb In January this year and February was my last month. On March the 20th I was charged for a unusual amount. Through phoning and waiting for the call center. Being forwarded from department to department was able to figure out i was being changed AGAIN for work done in October last year. I have tired numerous times to have this resolved but no one seems to have any idea why i was charged or how to reverse it. Everyone claims they will find out and call me back an no one does. Can the charges please be reversed.