You may have noticed that your SMS campaign used more credits than you were expecting? For example you select 200 recipient contacts for your campaign but it uses 400 credits.
A: This is because your message exceeds 160 characters and for each set of 160 characters a credit is used. You can add up to 900 characters per SMS message but just bear in mind that situation with deducting credits.
When drafting your sms message just look to the right of that edit screen to see the credits you are about to use per send.
If you send a SMS campaign which uses more credits than you currently have, then your campaign will still be sent but you will go into a deficit credit situation. You can easily rectify that by buying additional credits online.