This numbers called me periodically, never leaves a message or anything.

Keeps calling and wasting all my minutes! Never leaves a msg!!

They keep calling my cell they never leave a message and when I call them back I get a fast busy signal its very annoying how can i block them???

This number has called me twice in the last 20 minutes, did not leave me a message.

The person said its from ruby casino. Scammers trying to get your credit card info.

This number is an automated call from a colletion agency enterprise. If you have blocked them or ignored them ( collection agency number ) in the past, they will try a random phone call from an automated phone line service ( that doesn't exist anywhere ) to see if you really exist or if you just ignore them. If you answer the call, then they know someone is using that line. If you don't then, they might stop calling you.