Charging multiple times for a single instilation

You installed and I paid for my instillation of a new fiber line in May. I subsequently have had 3 phone calls requesting me to settle my account. Each time I explain that I have paid in full, the caller says everything is sorted and I do not need to worry. I now receive an invoice which still indicate 3 instillation for the same property???

Please rectify this immediate, it is unacceptable!