Insufficient i phone 5s charger warranty

I've been using my i phone 5s for 14 months and am on my 3rd charger now which i bought from Carnival City MTN. When i went to the store after 7 months , they told me the accessories are not covered under warranty. Many other people i know have experienced the same problem with the i phone 5s chargers. Why would the cellphone provider i.e. MTN not implement a system to assist clients with regards to this problem considering the alarming rate of incidences. It looks like as a service provider (MTN), are only happy to see us coming back to buy more chargers which dont come cheap.