Discord

You should be able to use any phone number if you're just locked out from being suspicious. Phone numbers that are used for verification purposes (because they think you're a spammer or are logging in via VPN or whatever) do not get stored / linked to your account, they are logged separately and automatically removed from the database after their timer expires.

If you get an error that they are expecting a different phone number than you put in, then you are probably fucked, sorry. Depending on the error that's on the screen, you are looking at using this form: https://support.discord.com/hc/en-us/requests/new?ticket_form_id=360000029212

Make sure to select "Account Verification & Credentials" and then "Phone Verification", and lastly select the error that you encounter like "Error: "Invalid Phone Number".

Please make sure you choose the option that reflects what you see when you try to put in a phone number / your old phone number. Try to give them as much info as possible to increase your chances of them being able to help you. But I don't think it's guaranteed.

I suppose you never enabled 2FA then? This could have helped you because you get backup codes, but hindsight and all that.