HARRASING TELESALES CALLS FROM DSTV/MULTICHOICE

Over the past few months I have been receiving up to 5 calls a day from Multichoice/DSTV sales people. Even when I block the number it does not help because a different number is used each time. This is so frustrating especially when waiting for urgent calls and it's DSTV. I have downgraded my subscription after many years of being a subscriber and am at the point of completely canceling it as I am sick of this.