Faulty battery and phone

I had purchased a Zest T1 i have had this device for a few months, it worked perfectly in the beginning but for the last 4 months the battery is always dying- there is a flashing red frame as well, there has been numerous occasions where i have really needed to make a call and in a detrimental emergency and had no phone to use. I am truly disgusted,i have no words. please can Zest repair or replace this phone - i thought it was a good buy. maybe its one faulty phone amongst thousands but i cannot go on with this phone its terrible. Dianne