They didn't get your cell number.
It's an auto-dialer. If someone answers it stays connected and a live person comes on or they feed you a recording. If a live person doesn't answer or it goes to voicemail, the auto-dialer hangs up and dials the next number. Rinse and repeat.
Called today and said they got my number from a website affiliate I visited. Say they have a rebate card for use at a popular store, and I should press "1" to receive my card or press "2" to be placed on their "do not call list".