The username consists of the first few letters of the domain you signed up for, I notice that it doesn't match the current domain so most likely it does match up with an older account seeing as the current hosting is only a few days old.
Once your account is at least 7 days old, comply with the ToS and is using at least half of the initial allotted space you can request for upgrade to unlimited disk space. Your account is a couple days short of the first requirement so an upgrade would not be possible today.