Remember, you must keep a positive PSTN (Prepaid) calling balance in order to make and receive calls to/from the PSTN (traditional 10-digit numbers).
You can manually add credit to your account as needed. (Note that this can be performed anytime even if you have the Auto-Refill feature enabled.) In order to use this feature, you must have a credit card on file with your account.
Step 1: Navigate to the "Account" Tab and go to the PSTN (Prepaid) heading on the left hand side.
Step 2: Click on "Purchase additional PSTN credits."
Step 3: Choose the amount that you would like to add to your available credit balance by selecting it from the dropdown menu.
Step 4: Click on the "Purchase" link in the lower right corner to charge the amount to your credit card.
Once the transaction is accepted, the selected amount will be added to your available credit balance, shown underneath the PSTN (Prepaid) heading. You will also receive a receipt via email of the transaction, sent to the email on file with the account.
You can view your transactions of PSTN credit purchases by clicking on the "View transaction history" link underneath the PSTN (Prepaid) heading. Transactions are separated based on the month that they occurred in.