Pricing plans are based on how many unique contacts you want to email each month (see active contacts), and the number of total emails you want to send.
You will start paying from 301 contacts/month or from 3001 emails/month, whichever occurs first. If you stay below that limit, you will be on a free plan.
Your email plan will include an X amount of contacts and emails sent per month. You can see our price ranges here. If you reach one of those limits, you will have the possibility to upgrade your plan to the next pricing range. If you don't upgrade your plan, you won't be able to reach out to new contacts by email during that running billing cycle.
SMS instead is paid per use. The price of each SMS sent depends on the recipient's country and on the number of pages of your SMS. You can view our pricing plans and SMS pricing here.