Cannot dial your destination - FRANCE

Hello,

I have just bought a France sim (really pleased). I have registered it locally and have a French number. I am dialling 08448690044 but when I enter my number (starting 0033) I only get halfway through the number and it says it cannot dial my destination through this access number. Have called customer services and all they can say is the access number is working fine so there must be another problem, which doesnt really help me. I am due to go to France this week and hoped to give my number to relatives to contact me. My number is OK as it can be dialled directly. Thanks