Hi Mona
I am Dave, I will help you with this.
Well done for being suspicious, you would be amazed how many users fall for this!
This is a well known Tech Support SCAM do not click anything on that page and do not phone that number.
When this happens, open Task Manager (Ctrl + Shift + Esc)
On the processes tab, locate your browser and end task on that
You can then continue to user your PC and browse the Internet
This is caused by a browser re-direct on a page you are visiting, try to avoid any page that jumps out to this sort of page . . .
All they are trying to do is get control of your PC, they will cause your PC to become corrupt and then require you to pay to have it fixed and even though you might pay them, they will not fix it!