advice regards 'nuisance callers'

few reports of 'nuisance callers' offering services at doors ie cleaning products
standard advice regards unexpected visitors, ignore or politely decline if they refuse to leave call police.
'nuisance callers' are not necessarily malicious
if you do give money to 'nuisance callers' you encourage them to return at a later date 

article/ link; 

https://www.met.police.uk/advice/advice-and-information/asb/asb/antisocial-behaviour/annoying-phone-calls-or-unwanted-visits/