Damaged cell phone and bad customer service from manger

On 19 December 2017 I app**** for a new contract with Vodacom for a Samsung j5 pro. I advised the consultant that assisted me at the sandton city branch that this was a gift for my son. And the phone will only be opened on Christmas Day and should their be any out of box issues this will still be under the 7 day Guarantee. I was advised that this will not be an issue. On the 26th of December 2017 I went to Vodacom in liberty mall where i went to purchase a screen guard and a cover for the phone the consultant try on 2 screen guards and there was a bubble on the bottom of the phone. Both screen guards had a bubble in the same place. I refused to purchase the guard nor the cover. On that same evening I had gone to Vodacom in gateway to try and purchase the guard and cover and to my surprise this happened again. The consultant tried in 2 covers and they both had the same bubble in the same place as previously mentioned. The consultant advise that this could be a defect on the phone. They could not assist me with a return as Vodacom is franchises owned and we had to take it back to the vodashop we purchased it from. On 27 December I called the sandton city Vodacom and advised them on the issue. The consultant I spoke to was Insistent that I had damaged the phone. He advised his manager about the it the manager then made an assumption that the guards were from a China mall or a knock off. I was immensely irritated by the statement and insisted that he come to the phone we then got into an argument and he eventually advised that I must bring on the phone. I was on holiday in kzn and therefore advised that I will go in on 3 January 2018. I have taken the phone in and the manager and I concluded that there was a defect on the phone. It has now gone for an assessment only to find out that there isn’t a defect. I refuse to pay for something that has a defect. I would rather cancel the contract if that’s the case. I will not be reliable for any cost involved and would like a full refund. If this is the service I receive from Vodacom I would have no other chose but to cancel all other lines that I have with them and will not be held liable for any costs involved.