I own two iMac desktop 21 1/2 inch I'm not using one although I keep the other one active.

Why do I keep getting telephone calls from Apple support telling me there's a virus? Is this true or not true? And they want to have control of my screen and computer. I'm a little skeptical.

These agents are persistent calling six or seven times a day and even have an identification number to give me I'm still a little skeptical

Thank you God bless have a good day