I dont own a cellphone and get by through borrowing family member's phones or asking strangers if I can make a call if I'm out on my own, it usually works out fairly well.
However whenever I run into online services that require a phone to make an account or whatever I usually get screwed- so I usually just use a family member's phone # if I know they'll never use the site or whatever or utilize a 10 minute/fake phone # creation site if I dont care about the site or service I'm signing up for.