Ever get a virus on your phone?

Yesterday my cell phone screen started flashing with a loud sound saying I had viruses. Now every time I use the phone , the text sound alert keeps playing multiple times all DAY from the virus page I assume. I guess it's saying to buy antivirus program but I am buying a new phone soon so not doing that. Anyone know how to stop this sound alert ? And should you install a free antivirus on a new phone?