Mobile Device Issue

I have been a Vodacom customer for more than 20 years and am absolutely disappointed in the service I received from Vodacom Trade Route Mall. My contract was up for renewal and I took a Huawei P30, after activating the new phone, the battery life was absolutely terrible, it wouldn't even last 24 hours, on a brand new phone. I called the Trade Route Mall branch to complain, took the phone back and was told to use it longer to monitor the battery life, nothing changed. I took it back and now they want to send the phone in for repairs, a new phone with a battery issue. Why can't the phone be replaced? I admit i did not unbox the phone when I got it, but surely you are able to see when the phone was switched on and activated. The phone is problematic, if you can not assist, I will cancel all my contracts with Vodacom and move to another service provider.