I WANT MY MONEY BACK OR A OTHER CELLPHONE

It's been 2 weeks and counting since I've taken back my premio X91 cellphone that just keeps shooting off after I get it back and have it for a month. I've been to the store and the way the manager Richardine handles my situation is not impressive. The cellphone was taken out of the display cabinet in my presence and boxed in the storeroom. When the fine shot off after a month and didn't go on , I took it back and in exactly after a months use again, the same thing happened. I am a student teacher and lose so much work . I asked the manager if it's possible that I get a other cellphone of the same value or my money back, she rep****"no" . I asked , so what do I do when the warranty expires and the fkne shot off..she grinned and said " you bring the fone back". HOW DO PEOPLE BECIME MANAGERS OF STORES WHEN THEY CANT ASSIST PEOPLE ?? EVEN THE CASHIER SAID THEY SUPPOSED TO REFUND ME??!! THIS IS FRUSTRATING AND I NEED THIS TO BE ADDRESSED