I've been having some problems with my PC lately
I think this intrusion is a result of the "problems". It looks like you picked up an infection, the purpose of which was to cause problems and pass your details to some outfit so you could subsequently be conned into parting with money to "repair" a problem that was caused for that purpose.
Or maybe I'm just cynical.
Your name, address and telephone number could have been obtained in several ways - and if "they" have that much information I would be wary of any online banking etc..
Assuming an infection, he most secure way of dealing with this is a complete deletion and re-install of OS (after backing up data and user settings). You can also try running a good anti-malware program (e.g. Malwarebytes), but you need to be confident about what you are doing. See the recent
http://www.pprune.org/computer-inter...-shutdown.html thread for example.
SD