We've been in our new house for over 18 months now - we are still getting postal mail for one of the previous occupants.  Note that previous occupants declined to offer a forwarding address.

I've diligently been writing on the letters "Return to sender, not at this address", etc.

I've tried calling the 0800 number, only to be met with much confusion, and still the letters come. 

The 0800 number suggested I take the letters into the Vodafone store - which I've done ... and the second time around they suggested there is nothing they can do.

So, in desperation, what do I need to to get these letters to stop coming to us (and hopefully get to the correct place)?

Is there a vodafoner lurking here that could perhaps help, please?

Thanks!