On the first page, there's the claim:

  Encrypted Calls
  
  All calls are encrypted with TLS 1.2+ for signaling and SRTP with AES-128 for audio. Your conversations stay private during transmission.

I would consider re-phrasing this so that limitation is more clear, for people who may misinterpret that encryption claim, unless you've found a way to encrypt PSTN signalling and audio which would be a much more impressive feat.

You are right, I will change that now so I don't mislead users.

Thanks for flagging this.