If you are not sure that all contacts from your Viber campaign list are actually using Viber, we suggest that you play it safe and enable the special Send as sms option when creating a campaign.
You can do it switching the Send as sms switch to the active position on the Send Viber page when editing a new campaign.
After you have switched it, specify:
- sender name for sms;
- the text of the message that the user will receive (here you can use the pre-saved templates, as when filling out the text for a regular sms campaign.