Hathway boradband - Harassment by hathway call centre

Last month , i had paid the amount twice mistakenly . I had left it considering it would be utilised for the following month ( jan & Feb ). I had received an invoice through mail . But on January first i had started receiving calls on payment due and then recorded message stating the connection will be barred . One side if i had checked with the call centre , thay say that due date is on feb ** th **** . I had asked them to share their managers Number Mr.Manikandan ********** , he does not picks the call . Still i get ** calls per day on due and deactivation . Kindly resolve the issue and i demand an apology for their unruly behviour and untimlely calls .