contract cancelled yet im told i am owing

Before the end of March this year i had an accident with my car hence i called Netstar to cancel my contract as i wasnt gonna be using the service anymore. It was a 3 year contract and i had about 7 months left. A consultant sent me an email and ccd the relevant person. Then i received an email stating effective 31 March 2015 my contract will be cancelled, i will no longer be liable to pay anything to Netstar and they will no longer provide me with a service. About a month later i got a call and I was told I owe R689.80. They started calling me and each time i told them i have cancelled my contract and have confirmation from them that its cancelled and I dont owe them. Even a debt collection company called me and I told them the same thing and sent them the proof<br> At 21:48 pm today i received this sms Credit listing notification. Pay R689.69 ref *** into Absa acc *** by 26 September 2015 or call Netstar on *** for payment arrangements. Please ignore if paid. My question is , how do you cancell a contract and then decide after sending me a cancellation that its now no longer cancelled? Are you even allowed to sms me at this time of the night? <br>