Harassment over Bradlows paid account

I've had an account with bradlows for a while now, when I purchased the last item I thought using the same method I've been using which was paying using my ID no would work out as it has been advised by their sales team however today I'm harrased by collectors telling me my account is handed over which I'm certain is overpaid... I've requested them to assist several times however I still get harrased by ADRS who threaten to send me personal collectors.