unauthorised upgrade by vodacom sales reward

I received a call earlier this year from Vodacom sales "rewards"saying that on my data sim "router "they will be adding 50 gb instead of 20gb that i was getting for the same amount i was paying since i was a valuable loyal customer ...i agreed because i had nothing to lose number : ***

in our conversation i told the lady that don't want an upgrade since i wanted to install a fibre ,on my surprise i just find out that this number was upgraded without me knowing now i want to install airfibre from vodacom ....where would i get money to pay 2 internet service to same company...i

i demand that this contract be cancelled without any cost.

thank you