They want me to pay for goods I didn't receive

I want to complain about this Jacklin Enterprises (Deagostini). My Subscriber Number: 4B001511<br> It is years now that I received items from them by courier which I ordered from them. On 6 May 2015 I paid an amount of R399.10 for goods received, and after that I didn't receive anything from them again. They keep on sending me emails and sms's to remind me that I owe an amount of R 469.00. I sent them several emails, called them also to ask for the proof of my signature where I \signed"for the goods received"