The great advantage of a partially or fully automated SMS API is that you don't have to look at it all the time. Hence, it can easily happen that the current credit is short or exhausted, which of course means that no further SMS can be sent.
So it makes sense to activate a notification that tells you when your credit is running low.
First you have to be logged in to your account and select Finances on the left to get to the overview.
A click on "low balance alarm" opens a popup, which allows you to activate an automatic notification by e-mail. You can specify the account balance at which the notification will be sent and the email address to which the notification will be sent. You can also specify several addresses, separated by a comma.
Then confirm the input by clicking on "Save", and voila: From now on you will be notified as soon as your account balance falls below the specified amount.