I picked up and got a computerized voice saying I have been randomly selected to win some air miles or aero plan or something and to press 1, seemed scammy so I didn't

Usage of CPE (Customer Provided Equipment) means that the caller-ID information has been set by the caller. ?Thus, they can call you, while they are showing a "not-in-service" number.  So, because the number is "unassigned", no telephone-company (Bell, Telus, Shaw, et cetera) can route the number back to them.

Got A Call with No message and told out of service when called back

Calls my cell phone - goes to messages and nevers says anything - just uses my minutes tha I pay for STOPSTOPSTOPSTOPSTOP

They called my office number; I did press 1 and when the rep came on - some promo company -  asked how could he help and I told him to remove my number from all future phone call solicitations.  Said he'd do it (would take 48 hours) ..... now time will tell.

Just got a call from them myself, didn't get to phone in time to answer, I was frantically trying to get to the phone cause looking for work it's a sell I bought just for the purpose of job hunting it's a unlisted number. ?I did check into 403 area code and it's from Alberta somewhere:)