If you ever see this message while you are adding a contact, it could mean that the contact has opted out. Only opted in numbers show by default, but you can toggle the filter on your Contacts page to see which numbers may be opted out.
Filtering Opted Out Contacts
To see which numbers are opted out, go to Contacts and click Filters. Then, select Opted Out in the drop down menu for the Status section.
If you see the contact you are trying to add is there, this means that they will have to opt in by texting in your keyword.
How to Opt In Using a Keyword
Your keyword can be found under Keywords & Numbers on the left panel in your account. The recipient you are trying to add to your contacts will have to perform this action of sending a text that includes your keyword to the short code phone number on the account in order to be added to your contact list.
Here is an example of how this works:
The demo keyword on this account is EZABC10413. There is a free demo keyword applied to all EZ Texting accounts using the EZ prefix. The short code number on this account that sends out texts is the number, 474747.
So, if a number that has opted out from this account and needs to be opted back in, that contact will have to text in the keyword from their phone to the short code phone number on the account.
After the contact has texted in the keyword to the short code phone number on your account, they will receive an auto-reply. If that reply says, "service access denied", then they will have to reach out to their phone carrier to remove what is called a short code block.
If the contact has successfully opted in or you see the keyword they texted in your inbox, then you can add them to contact group on your list.