Poor after sale service

I have had a cell phone contract since 2013. All was going well with my contract but untill i upgraded my contract late last year to an iPhone 6 plus.

The phone has been giving me problems since the word go. The phone would freeze, loose signal from time to time and the camera had a line through it. I couldn't be without a phone and so i never brought it in. Early March this year it stopped catching signal and i brought it in on the 7th of March. I made a follow on the repair on Saturday the 17th only to find that Cell C had a quote of R12500 because they wanted to offer me a iPhone 8 plus. It doesn't make sense that they would quote me for an iPhone 8 plus when all i want is for my phone to get fixed. The is a massive prive difference between these phones and surely that should say something about my affordability. If i was able to afford the iPhone 8 plus i would have bought it from the beginning I feel like nobody truly wants to help. They have pulled up this impossible quote so they can avoid fixing my phone this is by far the worst after sale service i ever received from any service provider.