Vodacom ******** people

I recently upgraded my dads Vodacom contract after 2 years, he recently left work so he’s currently employed part time. I upgraded his account mainly due to this, to my knowledge, he pays R269 per month because that’s what the contract states. His bill came through and it’s a staggering R394. I need to understand how this happens, he currently pays for his contract and we’ve said that R269 is affordable per month. He’s had it for just under a month and I’d like to give it back because it’s unaffordable now.