Xiaomi redmi 15c phone freez up put icon on my keyboard and it is not a workhorse

Hi i buy a redmi Xiaomi 15 c 4g i unhappy this phone is getting stuck freez up and stall i have been back to the branch in Hartbee****rt with in 7 days and thy refuse to help me so i am stuck with a useless device and its hurting my business as my phone is my income i wanted a refund i went back to the store before 7days contact me to resolve this ***