Throttling uncapped 4mb line speed

We have a 4mb line that's been working fine and suddenly on Monday, the maximum speed I can download at is 20kb/s which is absolutely ridiculous. Phoned the call centre and they explain that a certain amount of gigs is allocated to everyone on this 4mb line and once everyone(neighbors etc) uses the amount they begin throttling speeds. So apparently I don't need to use my Internet before it's throttled and to such an unrealistic speed. Why sell a data package as uncapped and then cap the speed? I believe that is not transparent business and kind of immoral. Having to go a week basically without Internet leaves a bad taste. All I can hope is that all resumes as normal next month and this is policy changed. At the very least a little more transparency in the way they conduct business. I would appreciat that.