Problem with signal with Huawei P Smart 2018

I bought a Huawei P Smart 2018 a year ago and I was using it without an problems and suddenly after 5 months of use it became having signal problems. At times the signal can go off during a call, sometime it is there and sometimes its off. I changed to P30 lite tge same service is working properly. What can be the problem and how can it be fixed