replacing phone

i bought P SMART 2021 phone and it has a factory fault and it keep on switched off and i took it to HUAWEI MELROSE ARCH they keep.on changing mother boards now is the fourth time replacing same mother board ,i ask they can't they replace the phone is it is keeping on same problem and the replace mother board ,half of the time since i have this phone is not working and i ma paying for it , now i took it for the fourth times they say i must pay R2200 becouce it cracked screen ,but my main problem id the dead phone not a screen