Iphone that is not working

Good day. Ive bought an Iphone late November 2019. I put on my email number when i restart rhe phone and suddenly the fone blocked. I went to Mtn in Schweizer Reneke the next day ro report it. They took it for repair. Today 2020 i went ti the Mtn store only to be informed that MTN says i must so it mysef. I even requested them to change it and i was told i they cant. I was told to repair the iCloud because mtn cañt assist me on that