Regarding my so called outstanding tv license

I was contacted in February this year regarding my so called outstanding tv license. I mailed them the proof of payment. I always renew in November each year. The last 2 months I started to receive threatening calls from debt collectors. I forwarded all proof of payment to them. Received an automated response: they will contact me in 30 days. I do not want my name to be black listed as I have a very good credit record. I can't seem to get trough to them. I sent an sms to a number advertised on the radio on day. According to message, my account balance is nil. (18/8/2017) On 8/9/2017 received sms from VVM to inform me that my account has an outstanding balance of R477.00. How on earth did they get that right? Does anybody at SABC tiv license know what they are doing?