No service issue in my iPhone

Hi, hope you are doing great! I’m using iPhone 11, I was on phone call and suddenly on the top bar of my iPhone was written “no service”.

my phone is PTA approved, I contacted my network provider and they said there’s no

issue from there end! Is this hardware problem or software problem? Please help,

i really hope that apple will consider my request. Is this my fault, I’m so worried and upset