Безопасен ли simarc.co.uk?

This company manages the ground rent for my flat. They were sending the bills to a completely wrong address for 4 years while I was out of the country, when I eventually managed to get them on the phone, having returned to the country, and tried to resolve the matter, they wanted to apply a load of extra legal expenses. I tried to explain that the error was theirs and they were very rude and spoke over me on the phone when I was trying to explain the situation. They demanded I put my case in writing, which I did. I have written to them three times since (at all 4 email addresses I could find for the company) asking for a response or at least acknowledgement of my email, and have still yet to receive a reply to my offer to pay them!