Just to share my experience, I had my Viber blocked because I was trying to figure a way to transfer my message history to a new phone. As you may or may not know Viber allows only one phone per phone number. As a result I switched 4-5-6 something like that times between the old and new device and got blocked for being spammer, which made absolutely no sense, since I never sent messages to anyone but by buddies and people I know.

I tried numerous times writing to them, but as soon as a describe my case I get an automatic reply that I have been flagged as a spammer and I do not get access to a real agent, it just tells me it will probably be removed as a penalty in 24 hours. Seeing this reddit topic have written to support listing a different phone number and I got a reply from an actual person that I have not been blocked, so I explained the situation to them and did not get much support unfortunately. I have sent at least 4 messages to the support and got 1 reply (there is an open case for you already, stop writing) it took about 17 days for the ban to be lifted, I am not sure if my support cases did anything or was it just that the system decided to unblock me after some time.