Getting charged data even when on WIFI

Ive had my 3G for a bit over a year now and havent had any issues with it up until now.

Currently running 3.0 and use Beejive and Facebook apps linked with my Wifi at home... also have few games on there and my phone is JB'd

I have pre-paid or pay as you go which ever you prefer style contract and topped up 20pounds on 4th and have only Txt'd about 10-15time since then and i never really call anyone maybe 1-2 time a month.

Went to Txt someone today and it error'd and once i checked my balance i had 0 credit which confused me no end because using that much in 4 days would never happen. So i checked my bill online and found this.

5 Pages worth of DATA charges for 0.01p every 10-30min.

I dont use the net on my iPhone unless its wifi at home so i dont understand why im still getting charged.

I rang the company im with and they didnt have anyone that could help me but he said there could possible be a setting in the phone that i need to switch on / off ?

Any help would be appreciated ive never noticed this problem before so unless its a new app ive added in the last couple of weeks thats doing it i dont really know.

If theres no setting for this i think ill just end up restoring it back to 3.0 and re JB'ing it.


Thanks in advance for any help
James