Cellphone

Good day, my boyfriend bought a phone at CNA, the first day the phone was fine but next day when he charged the phone its getting extremely hot, CNA eikestad mall replaced the device, the new one is doing the same. We were advised that we cannot take another device or get a refund... because he cannot work with this broken phone he's using it for work purposes. The phone is still in its 7day OBF period. We buy a brand new phone but it not satisfying our needs.