Telephonic Upgrade Offers - NO THANK YOU!

With so many ****s, Vodacom still insists on phoning their clients to offer upgrades on their packages. I've had it with these condescending youngsters, who cannot even pronounce my name correctly, phoning me and really pushing hard (to the point of being rude) for me to upgrade. Why is it so difficult for Vodacom to follow these offers up with a written contract? Oh yes, I know why - then people will see the fine print and change their minds.