Terrible service experience

Received a call from vodacom sales on the 1st of August 2019 for a phone deal, was planning on getting a new handset so it was good timing and convenient. I had an option to choose between a Huawei Y7 lite, Y5 lite and P20 lite. The sales lady practically sold the y5 lite more, touched base on the Y7 and said nothing about the p20. I ended up agreeing to the Y5. after the call I decided to compare the three handsets online, only to find out I am more interested on the p20 which she didn't sell to me. Called them soon after to change the deal but was told everything was processed and they can't assist. Received the phone the 7th of Aug, the next day I receive notification from my bank that a debit order has gone off. What I was told during the sale was that installment will start month end, Now I'm stuck with a phone I do not want on top of that they just debit whenever they feel like it. I've been a loyal vodacom client for years even though their tariffs are absurd and not to mention how expensive their data is. I'm beyond disappointment and angry.