Sharepoint - Custom URL for sharepoint Online

What @bonm014 said is true: it's not possible. The Microsoft's User Voice channel is the source for requested features and their status. Changing the tenant's name is one of the often requested additions, and it's current status is not implemented. Microsoft hasn't also added a status for the request (such as "thinking about it" or "working on it"), so there's no reason to currently wait this to be implemented.

As others at the given link have stated, it has become necessary to find an alternative when changing the URL has become a required matter. Real-life workarounds tend to be a set up of a new environment and migrating to it.

No it is not possible, except for building a new tenant with the correct url/name. This is the reason a lot of migration needs to take place within SharePoint Online.