Cancel my tracking device account!!!!

I called Netstar call centre in 2015 to let them know that I need my contract for the tracking device to be cancelled. The person that I spoke to assured me that it will be cancelled, however the debit order still ran. I then stopped the debit order from the bank and now in 2016 I get an sms informing me that I need to pay the R75 or be blacklisted .Really? I then called the number noted on the sms *** and the agent I spoke to simply said I need to either pay the amount or give her the name of the person I spoke to as there is no note on the system. What is the use of having agents that do not care and do as requested.