How do I remove Activation lock on my iPhone?

You could try a few things. Please note that some of the steps remove the data on your iPhone!

If you can't remember your iPhone passcode, you can erase your device using recovery mode:

• Using a Computer:
  • Connect your iPhone to a computer using a USB cable.
  • Open Finder (macOS Catalina or later) or iTunes (macOS Mojave or earlier, or Windows).
• Put your iPhone into recovery mode:
• For iPhone 8 or later:
• Press and release the Volume Up button.
• Press and release the Volume Down button.
  • Press and hold the Side button until the recovery mode screen appears.
  • In Finder or iTunes, locate your device and choose Restore.
  • After the process completes, set up your iPhone and restore from a backup if available. Apple Support

Then you should be able to set up a new Apple ID:

If you're unable to recover your Apple ID, you can create a new one:

• Go to Settings > Sign in to your iPhone > Don't have an Apple ID or forgot it?
• Follow the on-screen instructions to create a new Apple ID.

If you want to reset your Apple ID password, you can do so on the official wesbite:

• • Visit iforgot.apple.com.
  • Enter your Apple ID email address.
  • Since you don't have access to the trusted phone number, select "Don't have access to your trusted devices or can't receive verification codes?"
  • Follow the prompts to verify your identity and reset your password. This process may take a few days, depending on the information you can provide. Apple Support

Once that is done you need to remove the activation lock:

Activation Lock is a security feature that prevents unauthorized use of your device. To remove it:

• If You Can Access Another Device Signed in with the Same Apple ID:
  • Go to iCloud.com and sign in with your Apple ID.
  • Click on Find iPhone.
  • Select your device from the list.
  • Click Remove from Account.
• If You Don't Have Access to Another Device:
  • Contact Apple Support for assistance. They may require proof of purchase to verify ownership. Apple Support

I hope this helps you regain access to your iPhone.

If you do not know your password, and if for some reason you changed your number, you’ll need to try account recovery. How to use account recovery when you can’t reset your Apple Account password - Apple Support