Got an SMS from MBDCS - Overdue Account?????

I've sold my Golf 5 a few months ago and reported this to Altech Netstar. Got an SMS today from debit collectors that my account has been handed over to MBDCS. <br> <br> My account is apparently R1600 in arrears???? What is also strange is that Altech Netstar use to debt my bank account so how do Altech Netstar come up with an amount of R1600?<br> <br> What is also concerning is that I cancelled my subscription months ago so the question is ... was it really cancelled?<br> <br> This in unacceptable practice!