Until recently I was the user of a Wileyfox Swift 'phone. It was a 'phone about which I was enthusiastic, until the day when the demise of the Cyanogen organisation forced Wileyfox to produce their own version of "stock Android", since when a few things haven't worked quite as well as I'd like.
Thus when my 'phone started sending EVERY incoming call (either SIM) direct to voicemail, I blamed (wrongly, it now seems) the Wileyfox software. Wileyfox support were much more supportive than I had expected, but the only way they could help entailed me sending the 'phone to them. Wanting the quickest fix (and not wanting to be without a 'phone for an indeterminate period) I bought myself a new 'phone (Moto G5 plus).
After a few days of moving SMS and WhatsApp messages (etc.), the very last thing I set up in my new 'phone was the call blocker within Avast Mobile Security. I had sent a query (direct from my 'phone) to Avast about whether it was possible to migrate the blacklist from my old 'phone without retyping it. Although the reply was not what I wanted to hear, it arrived commendably quickly.
Now that my old 'phone was "spare" I decided to do a bit more debugging before sending it back to Wileyfox (and in the process remove as much personal information as I could). Having checked that it was still rejecting incoming calls the first action I took was to uninstall Avast Mobile Security. And now incoming calls were accepted !
I replied to the email from Avast with details of what I had found. TOTAL SILENCE !! Eventually I decided to raise the issue from my 'phone (the same way as I had queried the transfer of blacklists), but I just can't find how I did that ! After much puzzling I can only think that my new 'phone was using a free trial of "PRO" (now expired) which had allowed me to send the query. Is this a good time to try to sell me a PRO subscription ? Not really !!
If I am miffed about having bought a new 'phone when I didn't actually need one, I'm now angry that Avast don't seem to care about this problem. My confidence in Avast generally has evaporated. I had been very willing to help debug this issue, had sent Avast my blacklist plus details of some "weird" entries that had made their way into the list (how ?). Now I just want to find a different call blocker app (and probably antivirus as well).
Before I go I ought to add that though most calls get through on my new 'phone, I have seen one call sent unexpectedly to voicemail, this leaves my confidence low but of course gives no realistic chance of debugging. On the old 'phone maybe the first call after a reboot would get through (if it arrived within 30 minutes or so), otherwise ALL calls went direct to voicemail. I still have the old 'phone, it's accepting calls, though after uninstalling and reinstalling Avast my blacklist is empty. I could enter the blacklist again (recreating the "weird" entries from memory as I didn't copy them to the new 'phone). Even then I don't know if the problem will be recreated at the same level, but I'm not even going to bother trying if Avast aren't interested.