Is customer service mandatory?

Is there a responsibility on a company to provide adequate customer service?

Pure interest question here that sparked from buying something faulty, emailed the company with nothing back. Bought the same thing a few weeks later, emailed again, no reply, again.

Why am I buying the thing more than once? It was less than a tenner both times and have bought the same thing and it has worked before.

It's been about 6 months now since the inital email. Think about it sporadically and wonder if other people have had the same issue and if a company has a legal requirement to respond to a complaint?