To change the contact details status (for example Optout the Contact from the Platform or cancel the Optout if they wish to be reinstated) go to the Contacts Management area, accessible from the Platform toolbar:
or from within the SMS module:
Once you are on the Contacts screen locate the Contact you wish to make the change in relation to.
Hover over the Contact on the grid, you will notice a lock action icon appearing, press on the icon:
This will open the status window in which you can make the required changes by pressing on the toggle and entering the necessary details:
When done press Update and the changes will come into force.