I have no computer and my phone offline

Ask a friend, acquaintance or family to use their computer, or at a public library.

Alternately, visit your local Apple Store or Apple Authorized Service Provider and they should be able to help you out.

You will first have to make an appointment due to the pandemic.

Call Apple in your region see: Contact Apple for support and service

Contact Apple for support and service - Apple Support

Have you contact your carrier?

Contact / visit your carrier, ask them to help you.

Do you mean you can use your iPhone now?

See -> If you see an iPhone or iPad unavailable message or Security Lockout screen

If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support

You don't need a computer.