Billed for phone calls - we don't have a phone!

[#1]

My latest bill shows that we've made a phone call in January, but we don't even have a fixed phone in the flat, so we definitely didn't make any calls and are not planning on using plus net phone services. We only use the broadband. Please correct my bill and secure my account.

The question system or the chat systems don't work and I don't have time to be put on hold for hours as usual.

Moderators Note removed phone number from attached image (Dvorak)

[#2]

Sorry to see this, I've just responded to the ticket you've raised to address this. Here'd a direct link: https://www.plus.net/wizard/?p=view_question&id=187795922 - Adam 

[#3]

Hello Adam, thanks for your response.

I am not confident in your security around this. I've seen multiple posts on the community forum of clients who have been charged for calls they haven't made.
I need to be sure this isn't going to be happening again and that our line is secure from interference.

[#4]

Hi there, I perfectly understand your concerns. 

The fact that this is an isolated incident rather than a repeated one makes it very unlikely that there would be a concern over security. 

I've responded back to the ticket on your account with more information.