incorrect trusted phone number

An unrecognized "trusted" phone number has shown up on one of my accounts. Because I do not know the full 10 digit number, I cannot start the account recovery process. A week ago the number on the account was the correct number. I'm not sure how it was changed or what I can do to get past it. Every screen requires me to verify the number that is incorrect and unknown to me to start any type of recovery or use Two-Factor authentication.