First, you should check to see if your CCG or Health Board funds SMS credits.
If your CCG funded allocation has run out, or you have to purchase your own credits, you can purchase more by going to the iPLATO Store to buy these online with a credit/debit card.
Buy credits on the iPLATO Store.
If you have further queries with regards to your credits, or you are not sure if you need to buy your own, contact Support via help@iplato.com