Google never said their phone support is for login issues and makes it clear you need to login for support, and the op (who is using a throway) said they didn't remember using a mobile number when signing up so it sounds like the problem is partly on them. If you've been a customer for almost a year and suddenly realized you don't have a number you can call for support, then there is no reason to be outraged since they never promised that in the first place before you signed up and you were too careless to look. They do have a help page regarding login issues:
https://support.google.com/a/answer/6335621