they are bound by distance selling regulations and other selling authories and MUST take your call.
Which regulation is this?
Probably the EU e-commerce directive.
Webshops need to provide customers a physical address one can go to in case of complaints, an e-mail address and at least one other communication method.
Doesn't have to be a phone number though.
There was actually a German consumer organization that went all the way to court to force an online insurance company to put a phone number on their website, and they lost.
Court ruled the "contact form" on their website, was good enough as secondary communication method.