Don't pick up the phone when you see the number. If you do and then you even listen to what they have to say, they'll continue calling back every week. They actually get rewarded for speaking to a person, even if it's for 30 seconds. Being polite ends up biting you in the [***].
An illegal business activity. The caller is offering to "repair and improve your home", but refuses to give the name and address of the company.
Probably that means removing your belongings.