I thought that internet calls were suppose to be cheapest but PlusTalk is way more expensive that the telephone service that I use now (http://telediscount.co.uk) over normal BT phone. No pre-payments - No account to open - No Extra Bills - No Credit Cards. I use it mainly for calling Poland for 2p/min while PlusTalk charges 5p/min. Phone calls to mobile phones in Poland (13p/min) are cheaper than phonecalls to any UK mobile network (15-20p/min). With telediscount you can cal Uk mobile networks from 5-15p/min.
How do these companies do this?