Just received a call from these lot too, but missed it. The reason people get a quick call that cuts off is because call centers use technology call a "Dialer" which automatically rings from a list of numbers and patches them through to sales staff. Sometimes there is not enough staff to answer the calls. Ofcom (the regulatory body), although a small percentage of unanswered calls to occur.
How to stop these calls (from UK call centers only).
Register your number with the "Telephone Preference Service" (TPS) -
http://www.tpsonline.org.uk/tps/Provided a company has had no previous business with you (eg. marketing calls), Ofcom stipulate that they cannot ring you. The "Dialer Manager" must filter out all TPS registered numbers from their phone list.
If the company makes too many TPS-registered calls then they can be fined a minimum of £20,000 by Ofcom, often much more. They are also technically required to compensate you £10 if they call you, but that rarely occurs.
Unfortunately, there are a lot of cowboys in the industry. If you are TPS-registered and get a call, ask to speak to the "Dialer Manager". Be polite and point out you are on the TPS list and to check they have filtered their database correctly. Under law, they are also required to
- give their trading name (not the name of the company they are trying to sell for) if asked
- not hide behind 'private number'
- not put the phone down on you
If they break these rules, you can complain to Ofcom via an online form.
Penalties are severe when they are enforced. Hope that helps!