I removed esim and cannot add back

Thanks for clarifying.

It still doesn’t change what kb1951 posted …

… you’ll need to have a replacement eSIM provisioned by your carrier.

Most carriers - but not necessarily all - make this pretty simple by providing you w/ a specific QR code.

You might also find this article helpful:

https://support.apple.com/en-us/HT209044

Could the OP mean that he “Removed [his] Mobile Data Plan”?

It “virtually” removes the eSIM provisioning by electronic deletion …

… just like we “remove” software or a file.

You can’t remove an esim. It is built into the phone. Contact your carrier for help with this. You need to get it activated by them.