Who called from 2564550868

Same, one ring.  I think it's a new scam to get you to dial them back.  Once you do, they know they have a good number that they can sell or use to scam you.  Don't ever call them back.

One ring no msg

One ring then it hung up. Called back and it stated that I've visited one of the websites and was selected to receive $100 gift certificate

Rang, no voicemail. Same number called a couple weeks ago too--same thing happened.

Yes it's a scam.  You call them back, it's on your dime, and they've now confirmed that they have a good number for you.