Correct me if I'm wrong

I'm sitting here as I'm writing this review with mixed feelings. I can't believe what I just went through with a network provider I have been supporting for almost over 10 years. Please do feel free to guide me in the right direction but I really feel disappointed, frustrated, manipulated actually mixed feelings like I previously sed. Here's my story. I upgraded plus took out a new contract with MTN store Tygervalley on 30 May 2023. Everything went fine quick and easy plus the agent was great. Left the store happy chappy with new device and upgraded contract. Two days after I bought screen protector plus casing (from different provider) as nowadays devices don't come with any accessories but cable. Then the problem started, when ever I receive or make calls the person on the other end can't hear me and I use to think it was a network problem up until I tested it out of curiosity and notice that it wasn't actually the network. Took the phone back as it was still under the 7 day return period policy. The device was then booked in after confirming that it was faulty and replaced with another similar device. Asking about the screen guard that cost me R250, I was told, we sorry but we don't cover that as it wasn't purchase from us. I mean R250 down the drain for a screen protector not evens a week old and all u could say was we sorry? It's not like I broke the phone, it was a factory default that was only picked up on a later stage. Not evens a discount maybe on there screen protectors or just replace mine as a good gesture for inconvenience to me. If this is the case, you just lost one of your loyal customers and maybe through this review a couple more.