When sending emails, it costs one email credit to send one email, and it costs one sms credit to send one sms. Each multipart SMS message uses a number of credits equal to the number of parts.
If you would like more credits, contact your account manager, or email accountmanagers@pure360.com.
They will also be able to tell you the different rates for credits (they are cheaper if you buy more), how many you last purchased and how many credits you are currently using.