Harassed by Telkom Upgrades

I am for an upgrade and I keep getting called by Telkom to upgrade. I have received roughly six calls from the beginning of this year. Each person that calls me, I tell them that I will not be upgrading as I am waiting for the new iPhone.

Surely harassing your customers does more harm than good? I now feel like completely cancelling my contract just so that I can stop being harassed. This is unacceptable.