CANNOT DEAL WITH THIS ANY MORE !!!

I AM AT MY WITS END WITH MTN - going to every single complaint avenue I know and going to do everything I can to cancel my contract after being with them for 20 loyal years. I took an additional contract and from the start the new Samsung was overheating every time I charged. On Saturday it would not switch on anymore. That's 3 days after receiving it. Phoned MTN and they said no problem just bring it in because its still under the 7 day refund or replace guarantee. So took it to Pavilion MTN immediately filled all the paperwork only to be told oh NO you don't get the replacement immediately we have to send it away first and only when they receive it will they send you a new phone. WELL !!!its a week later and all I get is excuses. I CANNOT OPERATE WITHOUT A PHONE !!! what good is your policies if they are all lies. I am so upset !!!