iPhone 14 has no sim restrictions but not able to connect to any network provider

Hello everyone, I have an ongoing problem with an iPhone 14 bought from an Apple reseller that stopped connecting to network provider about six months ago. The phone has no SIM restrictions.

After numerous discussions with the Apple technicians the conclusion was that the phone is fine but they said that I could have a unique case where a previous prepaid SIM provide has locked my phone.

As I said the phone is open to all networks and it clearly states ´no sim restrictions´ and I am not getting any message from any provider. It has been erased and restored, it was updated to the latest version but where it suppose to show network, it says ´no service´

I tried a physical SIM card and an eSIM but neither work. strangely on one occasion when I installed an eSIM from one provider and a physical SIM card from another provider, the phone connected to the network provider but I only got 2G or EDGE. I discussed the issue with my current provider, they said it the phone at fault.

I am about to give up to replace the phone, I am hoping someone can help.

Thanks

eChief