There are two features that you can buy credits for in Salestrekker:
Each organisation gets 100 SMS per User included in subscription monthly. You can spend this either by sending invitations to Client Portal, manual SMS or marketing SMS. If you spend all SMS messages, you can either buy credits in Settings or wait next month to get 100 new SMS messages per each user.
When you signup for Salestrekker you get 10 eSignatures included. After they are spent you can go to Settings and buy credits. Please note they do not recharge on monthly basis - sample of 10 signatures are available only once.
How To Purchase SMS/eSignature Credits
To buy SMS and eSignature credits, you have to be or notify organisation owner to go to Settings > Plan and billing details. In top part of windows you can click on "PURCHASE NOW" button to execute manual purchase of 1000 SMS package ($49.99) or 100 eSignature package ($49.99):
To turn on automatic recharging, turn on switch for automatic recharge. Then choose at which point would you like recharge to be triggered: