I've change my phone number and I can't access my account anymore

I've change my phone number and I can't access my account anymore

Hello,
As the title says, I've changed my phone number but the account need the code sent to my phone number to proceed to the mail box. When I choose the option that I haven't access to the phone anymore, it says I need to contact the admin account. But the admin account is the one I'm trying to access, it doesn't makes sense! How can I access the account now?