This explains the problem https://www.pcmag.com/news/voips-big-security-problem-its-sip?amp=true
This explains the problem https://www.pcmag.com/news/voips-big-security-problem-its-sip?amp=true
For it to happen at all means that some unsecure prototol was being used in common i.e. by both Messenger and EIR's voip.That certainly explains a problem with SIP if hacking is taking place, which I very much doubt is the situation here.
You should be able to log in to your router and see what devices are connected to it
Hi Páid, thanks for your input, yes when I spoke with the Eir Technical dept they did suggest that changing a SIP password was something they would do anyway just in case but they said as we were not on the same network that it was very unlikely to be the reason it happened.I don't think it's a problem with your or your neighbours WiFi. I think it's entirely possible though if Messenger and your VoIP provider use the same insecure protocol (SIP or another).
I'm not an expert in this area but you should be reporting this to EIR or Comreg.