Worst customer experience ever! I had cancelled my...

Worst customer experience ever! I had cancelled my account after my tenancy contract had expired and I had paid the final settlement bill. My account was non-existent but they sent me a bill after 30 days of cancelling and closing my account. Visited the Mall of The Emirates Branch and the supervisor was ignorant and disrespectful to say the least. Even though he admitted it was a system error but he said I will have to pay because it s on my account which was cancelled and closed. Complaint was raised and the technical team called me on Friday morning at 9am and I requested them to call later during the day. Instead the person said okay and I got text saying the case is resolved. Most pathetic customer service and ignorantly rude staff! Such a shame!