Out of Box Failure

I upgraded my contract in December and received my new Samsung Galaxy S10e. I charged the battery through the night and used the phone during the day for a WhatsApp here and phone call there and by 18h00 the battery was flat. I again charged it during the night and the next day without using the phone for even half an hour the battery was flat again. I took the phone back and I was told it is an OBF (Out of box failure) and they are sending it to Repairs. I said that I want another phone, but I was told Repairs will decide if I can get a new phone. I waited for a month to get my phone back (by the time it came back from repairs we were away on holiday). I collected my phone last week and I was told that Repairs said there is nothing wrong with the phone. I have used the phone for 6 days now, I charge it during the night and the battery is flat before the end of the day. My 2-year-old S7's battery performs better than my brand new S10e!!! Is Vodacom now expecting me to pay for the next 2 years a monthly handset installment on a faulty handset they gave me?