How do I change phone number in Viber from SIM1 to SIM2, when I only have data on SIM2? How do I change Viber phone number in a dual-SIM phone from SIM1 to SIM2, when my current Viber account's phone number corresponds to SIM1, but I only have data on SIM2? (e.g. when I have moved to a new network)

(The Viber doc does not say how to)
In Android &gt; Wifi &amp; Internet &gt; SIM &amp; network, Enable both SIM1 and SIM2. Set 'default SIM for mobile data' to SIM2.


Apparently Viber needs to see old SIM1 as well, to verify it corresponds to your account, before it will allow changing phone number. But SIM1 is disconnected and doesn't need roaming; all your data is now coming via SIM2. While you are in this in-between state, you will not be able to receive any calls or messages with Viber - but neither Viber nor Android won't actually tell you 'No network on SIM1'. Viber will not notify you it's offline (oh no, proper notification would be too easy...), it will appear as if it's online, except when you try to send a message it will just get silently delayed, or when you try to make a call you get a 'No Service' dialog (but it won't say which SIM, and even if you  do have service on SIM2 and SIM2 is enabled as default).

Close and reopen Viber. Go into Settings &gt; Account &gt; Change phone number &gt; New phone number &gt; Continue &gt; Continue (to prompt about spamming your contacts with your new number)


Type in the new phone number (from SIM2) and press Continue. Viber will attempt to message all your contacts but fail with 'No Service'. Ignore that. (Actually it's desirable to prevent Viber spamming your entire contact book)
Viber will send the confirmation code to the new SIM2 number. This should succeed. This is the crucial step.
Verify it worked by checking that the phone number at the top of the 'More' profile page (under your picture) has changed to the new one.
If this step didn't work, do it again till it works. Make sure you actually have data connectivity on SIM2.

In Android &gt; Wifi &amp; Internet &gt; SIM &amp; network, disable SIM1. (At this point you could power down and remove SIM1 from SIM tray, if you won't need to reactivate it again/soon).
Now, you apparently have to reboot your phone. (Quitting Viber and deleting its cache don't seem to be enough. Although the doc implies this is never needed.)
Restart Viber and everything should be fine under SIM2.


(None of this procedure is described in Viber doc &gt; Change phone number but should be. Possibly because dual-SIM phones are not very common in Europe and US.)