I don't know whether you have the slightiest idea on how annoying those loansharks can be.
Their harassment can be endless and frustrating. If you thinking that police can catch ALL of them, read through the news - how many raids conducted in the past year and how many hundreds (or thousands?) already been caught - but still, we are hearing those harassment news in the papers.
There isn't much you can do when they strike. When my flat was strike by one of these people, I called them up to reason with them, telling them that my tenant already moved out and no more staying in the unit. Their reply? "We only recognised the address, we don't care the rest. U want to live in peace, u pay up for him". The 2nd group who strike, after talking to them, told me to go make a police report and paste the report at the door. But he told me, "no guarantee they will do nothing".
Good luck and all the best.