Warrenty

I used to be at vodacom went over to mtn beacuse their service was beter for me. But now i am not so sure any more. I have an samsung note 9 24 months not yet over but i have to use speakee or earphones for people toe hear me when i make or recieve a cal decided to ask them toe semd it it for repair so phoned my nearest mtn store where they told me i would be liable for the cost of reparing my phone which is still under contract.... i then went to samsung website and saw that samsung has an 24 month warrenty on phones so why do i have to pay for the repair is mtn ******** me?????