Today, CallCentric has informed me that they have now implemented and support +888 United Nations disaster relief calling through the Voxbone iNum network.
I have just tested this feature by calling Voxbone's test numbers. And, all indications from my test calls is that CallCentric has implemented this service for free, just like iNum calling is free.
+888 network dialing differs from iNum dialing by 1 digit. iNum's are 15- digit numbers, whereas +888 numbers are 14 digits. And, just like dialing iNum's from North America, you will also need to add the + digits (or, 011 access code). This now means you will be dialing a 17-digit number, in total.
If you have a CallCentric account, you can test +888 dialing by calling the following TEST numbers:
DTMF Talk-back Test: