I received 12 voicemails yesterday from a robo caller claiming to be Apple support. It said my iCloud account had found suspicious activity on my iCloud account. Has anyone else been getting these?

Unfortunately, it is a very common scam attempt.

Apple does not make such calls.

All such calls are scams from criminals attempting to steal your personal and financial information. The callers will often use number spoofing to pretend they are calling from a legitimate business. The correct course of action is to ignore the calls or hang up on them, repeatedly if needed. 

Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams - Apple Support

Yes, unfortunately, you are not alone. I get them, my wife gets them, and other users here get them. These scammer are quite persistent. Here is a discussion from yesterday at where the user was getting multiple scam calls.

Calls and messages from Apple support

My sole telephone is my iPhone and I use the silence unknown calls setting. So while I see numbers in my log, they don’t leave a voice message so they then just go to blocked. And AT&T’s free Call Protect app catches some of that sort of crud too.