Paid bill and the next month in advance

So I paid June’s bill last month and at the same time (06/22) paid for this month. And yet I was billed and it tried to take the amount out of my account of which was cancelled, hence why I paid a month early to have time to sort the account out. I called and the rep did not understand and seemed to not know English well which baffles my mind. Any assistance would be so appreciated!