@merta 

May I know who is your ISP? Have you confirmed with the ISP that if the line is stable? If possible, test the line with another modem, ensure you have a stable internet connection from the ISP.

BTW, To locate this issue and try to fix it, we would like to follow up on your case via email.

@Kevin_Z 

I spoke to the ISS.  They said there was nothing wrong with my line.  The technical team came twice to check. Thank you, i am waiting.