I need to delete my old Apple ID which I have forgotten the password and trusted phone number for.

Connor_Laing wrote:

Ok I understand that, but it's asking me to confirm the phone number but I don't have access to that phone number anymore nor do I even remember it, and without the phone number I can't reset my password.

Ok, I did not realize that you did not know the phone number of the device. The Trusted Phone number set up on your Apple ID can be any phone number and does not have to be the phone number of the device, so I thought you just didn't remember what number was used for the Trusted Phone number. This support article discusses the same situation you are in and contacting Apple directly may be the only possibility. Those links are also provided in the Support Article.

I can’t remember the phone number I used … - Apple Community

Connor_Laing wrote:

Sorry, my current Apple ID is using a different email address than my old Apple ID, I would like to use the email address from my old Apple ID to log into my current Apple ID. I want to delete all the data from the old Apple ID, but in order to do that I need to log into it, but I can't because I don't remember the password, trusted phone number, or have the phone that I used that Apple ID on.

Ok, I think I got it. The one thing is that you cannot merge 2 Apple ID's, so you will need to choose the old one or the new one. You will not be able to change your current Apple ID to your old one and still maintain the data on your new Apple ID. Each Apple ID will always be associated with the apps/subscriptions/music and other data associated with it.

If you choose your old Apple ID, you just need to reset the password using the iforgot website in the previously provided link. You can then use that Apple ID and the data associated with it on any device.

You do have the option to create a new email address and change your Apple ID to that email address. This will allow you to keep any data associated with that Apple ID. You just cannot change it to a email address that has been previously used as a Apple ID.

Change your Apple ID - Apple Support

You will need to use the third option here to reset your password using the iforgot website.

If you forgot your Apple ID password - Apple Support

Not clear on "delete that old Apple ID". You still need to gain access to the Apple ID by resetting the password. Once you have access to that account again you can remove the old device by signing into iCloud.com. I think you now want to use that Apple ID email on a different device, so not sure on what you meant by deleting the old one.