A technician probably changed which port a cable plugged into back at the branch station. Unfortunately there's not much that you can do. Call the ISP, but I woudn't expect much out of them. Until you can show them that the connection drops that is.
They might be able to run a signal test from the tech center, or a connection on the cable lines might be getting corroded. Try unscrewing and resecuring all of the cable connections you have access to.