Express Transaction Services harrassing us with unsolicited shipments of POS supplies Montreal, Quebec

this company call 4 - 6 times per year claiming that we have made an agreement with them to purchase 1 years worth of POS machine supplies and every time ask/tell them if this will be the last shipment, they tell me our file is not yet closed. the last time was feb 27 and I was told teh file was closed but just this week got another call saying our file was still open and we are obligated to purchase the supplies. after bantering back and forth I finally got fed up and hung up. well I got another call today, same thing. I ended up giving him my managers # to call and hash it out with her. I have a feelilng its not the last I will hear from them.