Phone not receiving data

Hi, I’ve had my Apple refurbished phone for over a year now, when I first got the phone data was being received fine, everything was working fine then all of a sudden the phone just couldn’t connect to anything outside of WiFi, this went on for about a month. (Just to preface this that this isn’t a carrier issue, I’ve completely ruled this out) In the midst of having to inconveniently jump on people’s hot spots or WiFi in places to connect, suddenly it just started working again for about 8/9 months.

Then about 6 weeks ago, the problem started happening again, the phone still shows as “4G” or “5G” at the top so there’s no issues there but the phone just isn’t receiving the data which makes me think it’s an internal issue. I also recently holidayed in the Cayman Islands and bought an eSIM and still, no data being received through. It works every now and then but like I say this isn’t a carrier problem. It also briefly works for a minute if I switch my phone on and off. I have been in touch with Apple several times they have ran diagnostics and ended up putting the phone down on me because clearly they couldn’t help and had no resolution. Unfortunately my phone is out of warranty now,

Has anybody else had this issue and is it worth taking it to an Apple Store or getting a whole new phone completely? Also if this has happened to anyone else and they found a resolution please let me know.

I feel I’ve exhausted every avenue.

My phone is iPhone 13 Pro Max and my version of iOS is 17.5.1 Many thanks