Disgrace to a trusted customer after many years

I was ****** and could luckily upgrade. I went to Fourways Vodacom store and the sales lady ADVISED me to take the iPhone SE. she said I have 7 days to return the phone if unhappy. The battery is **** and doesnt last nearly as long as my iPhone XR’s Now they tell me I cannot cancel the contract and also cannot choose a new phone I need to take the same one if they figure out by some miracle what is “wrong with my 4 day old phone” this is bull****. My company also does business with Vodacom and they make a **** load of money from us. I will be sure to inform them of the ****py and unhelpful, unsympathetic service of Vodacom.