Hello Relk,
We understand that your iPhone wants you to set up an eSIM even though you don't have one. Is that correct? If so, can you tell us if you have an option to bypass the on-screen prompt? If you do, skip the prompt and let us know what happens.
If you don't have the option to bypass the on-screen eSIM prompt, try reaching out to your wireless carrier to see if they can help you to set up service without an eSIM.
Lastly, check out the links below if you'd like to learn more about an eSIM and how it works.
About eSIM on iPhone - Apple Support
Set up cellular service on iPhone - Apple Support
Please do not hesitate to reach out to the community if you have more questions.
Thanks for using the Apple Support Communities.
Cheers!