Hey @Assti - it sounds like you may have a faulty modem. As @petergdownload mentioned, it'll be best to test another device on your end to ensure it's not isolated to a particular device. We'd also suggest removing any other electronic equipment near the modem that may be interfering with your WiFi signal. For example, microwaves are a common culprit of this issue.
If neither of the above help, please shoot me a private message with the following info and we can look into getting you a replacement modem:
Are you the primary account holder: Y/N
Date of birth: