I’m having issues with my iCloud

You are sign in here .  .  .  with your Apple ID & Password (?).

Your Apple ID is the personal account you use with all Apple products and services. It includes the email address and password you use to sign in, as well as the contact, payment, and security details that you use with Apple.

You can’t merge multiple Apple ID accounts.

There is no SIM card in the phone, look for / visit a carrier, take a subscription, postpaid or prepaid card.

Checks whether the SIM card is suitable for your iPhone.

See this Apple article: How to unlock your iPhone for use with a different carrier

How to unlock your iPhone for use with a different carrier - Apple Support

-> Apple can't unlock your iPhone for use with a different carrier. Only your carrier can unlock your iPhone.

Then see -> If you can't connect or sign in to iCloud

If you can't connect or sign in to iCloud - Apple Support