From their site
"You just pay for
local call access rate
when you are on the net.
24/7 telephone support 0870 224 3494 " Local rate?
Can I get help over the telephone?
IofM.net's Premium rate telephone help number 0906 677 8866
(08:00 to 21:00 week days; 09:00 to 17:00 week ends, Public holidays excluded)
Will my BT discounts work?
Yes, you can elect IofM.net as one of your discounted numbers.The number is 0845 112 1366.
However this might apply to the dial up number.
Well at least 0845 is cheaper than 0870