I'm leaning towards no at the moment - mainly because the hackers appear to be based in a different country, and because they appear to be brute forcing the WhatsApp verification code API. Also, his phone could still do outgoing calls when he tried it earlier.

He said that he got a ton of SMS verification messages from WhatsApp and random phone calls from Argentina, Mexico and the US over the past few days that he was ignoring - not sure how they managed to bypass rate limiting on that.