International Internet bandwith drop to 1MB

We having now for more than 1 year a 5MB fiber internet connection from Mweb without any problems. A short while ago the connection dropped internationally to 1MB down. Locally the speed is fine on 5MB. After 2 days of calling and complaining about the issue, Mweb support couldn't fix the problem (they tried to offer us different solutions with no result). After speaking to our account manager we got informed that Mweb dropped the line to 1 MB (4:1) without informing us. In our contract is written \ The internet bandwidth is burstable for all internet traffic