iPhones cell data

At the top right corner of my iPhone xs the cell data waves just turn off randomly and I’m not in a dead zone and it’s happen a few times this month only I had restarted my phone when it does so when I restart it goes back to normal hut randomly does it again like in a week or few days…what can be down of this? And do I need to buy a new phone? I do not want to put any money in to fixing my phone, I wanted to wait to buy the iPhone 15 when it comes out next year