Vodafone Problem

[smurfchops]

I have a Nokia 6124 thru Vodafone on contract, for a week now. In the last couple of days, every time I dial a land line I get 'number not in use'. I dial again and it is OK. Is it a fault with Nokia handset, SIM or Vodafone? They are sending me a new handset as I still have a week's 'cooling off ' period, but will only give me another four days over the 'cooling off' period, rather than a new 14 day period, even though it will be a new phone. What do you think about this ? I have rung them three times and tried three different ways of sorting this problem, (the network lines on the left of the screen keep going low as well) but still not solved problem. I have done a Manual Roam, as well as taken SIM out, turned off and on, put SIM in again, then manual roam again, and I have gone into GSM mode. I live near Kingston, Surrey, not many miles out of London, by the way.