BT retail marketing letters

[#1]

Hi
Every week I seem to get a personally addressed unsolicited letter from BT retail offering broadband and phone services.
As my broadband & phone is with PlusNet and PlusNet is owned by BT retail, why do I get these letters?
How do I persuade BT to save their cash & stop sending these letters?
Thanks
Richard

[#2]

You won't  I even phoned them several times.  BT have your details, and they will forever have them, even if you request for your details to be removed from their database.
I had assurances my details were removed, yet continued to get mailings from them.
I used to also get "come back to BT, just fill in this freepost envelope", however they stopped sending me those, after I sent them all back with GO AWAY written inside, at their postal expense.

[#3]

When I complained to BT about sending me letters, they just dropped my name from the letters and instead addressed them to the 'Home owner'.

[#4]

Simply write not known at this address on the envelope, and return to sender, enclosing some other junk mail!! 
it will eventually stop, 

[#5]

I got some junk mail, not from BT, the other, i didn't open it, i crossed out my address and wrote on the front in very big letters "Undelivered, return to sender overleaf", after all it does say, "If undelivered, return to this address"

tim