Call interference / call mixed up

This is weird, I just got a IMO call from a total stranger who was having a conversation with someone else on imo. I could listen to the whole conversation, I kept saying "hello, hello, who is this?" but the other person couldnt hear me, it lasted 4 minutes until I finally hung up.
I just downloaded this app, what is going on? I shouldnt be receiving other peoples phone call conversation!

Suichic about imo video calls and chat, v6.7.1