mass organization disturbances (Bali)

About a month ago, there was a mass organization that came into the shop dropping off a proposal for us to look over and contribute every month. In return, they said they can be reached 24/7 should there be any security disturbances. They said the contribution was up to us to decide.
A few weeks later, they came back and demanded a contribution. When we said that we already contribute to the local banjar, they insisted that they are different. This causes some terror on my colleagues as well, as they would enter the shop with 5 members at a time.
Up until today, there have been visiting regularly, demanding the contribution that we are not willing to give, since their security service isn't professional. And from what I heard, they have caused problems elsewhere. Should this continue, it may cause an uncomfortable situation for my clients.
Does anyone know where I can get reliable security guard who can help neutralize the situation should there be something similar happening in the future?