Unhappy hisense customer

I bought a hisense f17 7phone last year September and for the past 3 months i have been having problems with the phone where it goes from fullly charged to swiching off completely wile im making a call or sending a text message.I also noticed the battery is a bit swollen and is very strange.I spoke to a lady at hisense who assured me that someone was gona contact me and she even send me the email that she send to the relavant people.I have not heard from anyone up till this moment and if i phone hisense customer care i get send from pillar to post and nobody even answer the phone at times...i am very unhappy as a customer and i make use of alot of hisense products in my daily life