Vita Interiors - is this a trustworthy company?  

Hello,
I am very glad that I found this forum, happy to be here!
I am living in Germany and I experienced some issues with the Uk-based company Vita interiors.
Unfortunatelly I have a warranty issues with one of their products. The base of a chair was replaced like 11 months ago, but now the bearings of the base are loose again.
But they only did answer once to my mail, after that I send some other messages but no response from Vita interiors.
How can I handle that? Suggestions?
Very kind regards,
Bernd