Endless harassment by Vodacom

For the last two weeks I have been absolutely battered to the point of exhaustion, by multiple phone calls daily - at all times of day - that my Truecaller app identifies as ''Vodacom Upgrades Department''. After the first call I blocked the number, but I kept receiving calls from a host of different numbers, all listed as Vodacom Upgrades. Blocking all of the numbers has no effect - the number simply changes each time. Today I finally answered a call and very impolitely asked the person if there was any way the calls could stop. His response was "only if you upgrade"! I can only assume that Vodacom has enlisted and incentivised a large army of *********, desperate, inconsiderate salespeople (who clearly work for commission), to endlessly harass their customers and impose upon their privacy.