Cheapest way to get a second cell number? Tello is $3.80/mth.

Going to get an Android phone to do some offers on, and I've been thinking of getting a second number to use as a junk number, like a junk email, to use on deals where you need phone verification.

Tello has 100 minutes talk, unlimited text, no data, for $3.80/mth for the first 6 months, then $5 after that. Anyone know of any cheaper options to get a real number?