Bad Service with a Vodacom Contract after Huawei P Smart 2019 screen got loose

This is by far the worst experience I have ever had. I took a cellphone contract for a Huawer P Smart 2019 in March, luckily a collegue also took the same phone. The screen became loose and detached itself, the same happened with my colleague's phone but mine became worse overtime, when we took the phones back to Vodacom 3 weeks back, we were assured that it was an Out of Box failure and we will receive new phones, as time went on we were not receiving feedback from vodacom and after following up numerous times, we were then told that my colleagues's phone will be fixed and mine is out of warranty because apparently it was taken elsewhere before taken to Vodacom, I still dont know how to prove that the phone was not taken anywhere else and how vodacom can prove that the phone was taken elsewhere. I mean it is my word agaisnt theirs and I dont have technical proof of what happened apart from their technical report. How do I know that all the things listed in the report did not occur after I submitted the phone? How do you justify the fact that both phones had the same screen issues and 1 got fixed. This is so appalling from Vodacom, I never expected such. Before you even get to the technical problem inside the phone, how do one explain how the phone got loose in the first place, the phone has no external damage, it has bever been dropped, it is in a good condition?