Unwanted sales phone call from Plusnet

[#1]

Had a Plusnet customer service person call me up just now trying to see if I was on the best package ( heard that one before  )
I failed the security check on purpose & she said I would be called later in the week when I had access to the security information.
Im on a legacy phone & broadband package, im happy with it & im out of contract, I dont want to change it.
Can a stop be put on Plusnet customer service calling me at home trying to sell me stuff / tie me in to a longer contract please?

[#2]

Modify your communication preferences in the Member Centre.
Link

[#3]

Thanks for the linky 
Nuked them all apart from email contact.

[#4]

Sorted. 
Thanks for update.