As a telemarketer, you run the risk of heavy penalties that can run into thousands of dollars. Federal Trade Commission (FTC) can fine you anywhere between $100 and $1,500 per every call that's reported, if you end up being sued. While that is the worst-case scenario, there is still the risk of your numbers being blocked.
Your caller id could already be marked as spam. When too many users mark your number as spam, the chances of your sales call getting answered go down drastically. That's because nobody wants to waste time talking to 'spammy' call reps.