Just been punished by Vox for continuing with their service.

I recently moved premises, and spoke to a Vox clinician about moving the line across. All seemed fine, and I was warned that I would be charged an installation fee if I cancelled the service in a month. I was made to believe that I was on the same contract -as no additional paperwork was signed. I was then this month charged a pro-rata amount PLUS my normal amount. How is this possible? Where does this pro-rata amount come from if I was only using one line the whole month?

Disgusting