Phone faults

I came into the store just before the lockdown with problems with my phone not making or receiving calls and having a very weak signal connection. They did a factory reset on my device and said to give it 5-7 days to see if anything changes it’s gotten worse, my calls still aren’t working all the time during phone calls I’m being told I’m very quiet and sometimes they can’t hear me at all occasionally since my lock screen has randomly started going black or just freezing to I know this won’t be the same problem or because of the factory reset it’s just another problem I’m struggling with at the minute