Telemarketers *can* call cell phones, as long as it's not done via an autodialer, and/or some sort of recorded message telling you to call back or hold for a representative. The same applies for collection agencies, but in addition, they cannot call your cell phone unless you
specifically gave them that number. If they obtained your cell phone number via any other means, it is
illegal for them to call you on your cell phone.
Also, if you don't want to get junk mail for "pre-approved" credit cards or general spam from insurance companies, you can opt-out at
https://www.optoutprescreen.com/?rf=t . Amazingly enough, the credit reporting agencies hand this information out to any company that requests it. That's how these places get your name and address and all that good stuff without your SS#.
And lastly, you can put your landline telephone number on the Do Not Call list @
www.donotcall.gov. Keep in mind that if you've done business with someone in the past, I believe that they can still contact you; and certain non-profit organizations can still call for donations and stuff, as well. But, it does cut out a good 90%+ of all "spam" calls.